Jack Mulanax of the Vallejo Police Department subsequently wrote Allen had received an other than honorable discharge from the U.S. Navy in 1958, and had been fired from his job as an elementary school teacher in March 1968 after allegations of sexual misconduct with students. He was generally well-regarded by those who knew him, but he was also described as "fixated on young children and angry at women".
On October 30, 1966, an 18-year-old student at Riverside City College, Cheri Jo Bates, spent the evening at the campus library annex until it closed at 9:00 p.m. Neighbors reported hearing a scream around 10:30 p.m. Bates was found dead the next morning, a short distance from the library, between two abandoned houses slated to be demolished for campus renovations. The wires in her Volkswagen's distributor cap had been pulled out. She was brutally beaten and stabbed to death. A man's Timex watch with a torn wristband was found nearby. The watch had stopped at 12:24, but police believe that the attack had occurred much earlier.
A month later, on November 29, 1966, nearly identical typewritten letters were mailed to the Riverside police and the Riverside Press-Enterprise, titled "The Confession". The author claimed responsibility for the Bates murder, providing details of the crime that were not released to the public. The author warned that Bates "is not the first and she will not be the last". In December 1966, a poem was discovered carved into the bottom side of a desktop in the Riverside City College library. Titled "Sick of living/unwilling to die", the poem's language and handwriting resembled that of the Zodiac's letters. It was signed with what were assumed to be the initials rh. During the 1970 investigation, Sherwood Morrill, California's top "questioned documents" examiner, expressed his opinion that the poem was written by the Zodiac.
On April 30, 1967, exactly six months after the Bates murder, Bates' father Joseph, the Press-Enterprise, and the Riverside police all received nearly identical letters. In handwritten scrawl, the Press-Enterprise and police copies read "Bates had to die there will be more," with a small scribble at the bottom that resembled the letter Z. Joseph Bates' copy read "She had to die there will be more," this time without the Z signature. In August 2021, the Riverside Police Department's Homicide Cold Case Unit announced that the author of the handwritten letters anonymously contacted investigators in 2016 and was identified via DNA analysis in 2020. He admitted the correspondence was a distasteful hoax and apologized, explaining that he had been a troubled teenager and wrote the letters as a means of seeking attention. Investigators confirmed that the author was not the Zodiac.
The Zodiac murdered five known victims in the San Francisco Bay Area between December 1968 and October 1969, operating in rural, urban and suburban settings. He targeted young couples and a lone male cab driver, and his known attacks took place in Benicia, Vallejo, unincorporated Napa County, and the city of San Francisco proper. Two of his attempted victims survived. The Zodiac himself claimed to have murdered 37 victims, and he has been linked to several other cold cases, some in Southern California or outside the state.
The first murders widely attributed to the Zodiac Killer were the shootings of high school students Betty Lou Jensen and David Arthur Faraday on December 20, 1968 on Lake Herman Road, just inside Benicia city limits. The couple were on their first date and planned to attend a Christmas concert at Hogan High School, about three blocks from Jensen's home. They instead visited a friend before stopping at a local restaurant and then driving out on Lake Herman Road. At about 10:15 p.m., Faraday parked his mother's Rambler in a gravel turnout, which was a well-known lovers' lane. Shortly after 11:00 p.m., their bodies were found by Stella Borges, who lived nearby. The Solano County Sheriff's Department investigated the crime but no leads developed.
Vallejo police served another search warrant at Allen's residence in February 1991. Two days after Allen's death in 1992, Vallejo police served another warrant and seized property from Allen's residence. In July 1992, victim Mike Mageau identified Allen as the man who shot him in 1969 from a photo line-up, saying "That's him! That's the man who shot me". However police officer Donald Fouke, who is speculated to have seen the Zodiac fleeing from the Stine killing, said in the 2007 documentary His Name Was Arthur Leigh Allen that Allen weighed about 100 pounds more than the man he saw, adding that his face was "too round". While Nancy Slover, who received the call from the Zodiac in the aftermath of the Mageau/Ferrin shooting said that Allen did not sound like the man on the phone.
On October 6, 1969, Allen was interviewed by detective John Lynch of the Vallejo Police Department. Allen had been reported in the vicinity of the Lake Berryessa attack against Hartnell and Shepard on September 27, 1969; he described himself scuba diving at Salt Point on the day of the attacks. Allen again came to police attention in 1971 when his friend Donald Cheney reported to police in Manhattan Beach, California, that Allen had spoken of his desire to kill people, used the name Zodiac, and secured a flashlight to a firearm for visibility at night. According to Cheney, this conversation occurred no later than January 1, 1969.
Just before midnight on July 4, 1969, Darlene Ferrin and Michael Mageau drove into the Blue Rock Springs Park in Vallejo, four miles (6.4 km) from the Lake Herman Road murder site, and parked. While the couple sat in Ferrin's car, a second car drove into the lot and parked alongside them but almost immediately drove away. Returning about 10 minutes later, this second car parked behind them. The driver of the second car then exited the vehicle, approaching the passenger side door of Ferrin's car, carrying a flashlight and a 9 mm Luger. The killer directed the flashlight into Mageau's and Ferrin's eyes before shooting at them, firing five times. Both victims were hit, and several bullets had passed through Mageau and into Ferrin. The killer walked away from the car but upon hearing Mageau's moaning, returned and shot each victim twice more before driving off.
On July 5, 1969, at 12:40 a.m., a man phoned the Vallejo Police Department to report and claim responsibility for the attack. The caller also took credit for the murders of Jensen and Faraday six and a half months earlier. Police traced the call to a phone booth at a gas station at Springs Road and Tuolumne, located about three-tenths of a mile (500 m) from Ferrin's home and only a few blocks from the Vallejo Police Department. Ferrin was pronounced dead at the hospital. Mageau survived the attack despite being shot in the face, neck and chest. Mageau described his attacker as a 26-to-30-year-old, 195-to-200-pound (88 to 91 kg) or possibly even more, 5-foot-8-inch (1.73 m) white male with short, light brown curly hair.
The decryption of the July 31, 1969 408-cipher by Donald and Bettye Harden
Zodiac's letter sent to the San Francisco Chronicle on July 31, 1969
Zodiac's letter sent to the Vallejo Times-Herald on July 31, 1969
On August 1, 1969, three letters prepared by the killer were received at the Vallejo Times Herald, the San Francisco Chronicle, and The San Francisco Examiner. The nearly identical letters, subsequently described by a psychiatrist to have been written by "someone you would expect to be brooding and isolated", took credit for the shootings at Lake Herman Road and Blue Rock Springs. Each letter also included one-third of a 408-symbol cryptogram which the killer claimed contained his identity. The killer demanded they be printed on each paper's front page or he would "cruse [sic] around all weekend killing lone people in the night then move on to kill again, until I end up with a dozen people over the weekend".
—The solution to Zodiac's 408-symbol cipher, solved in August 1969, including faithful transliterations of spelling and grammar errors in the original. The meaning, if any, of the final eighteen letters has not been determined.
On August 7, 1969, another letter was received at The San Francisco Examiner with the salutation "Dear Editor This is the Zodiac speaking." This was the first time the killer had used this name for identification. The letter was a response to Chief Stiltz's request for more details that would prove he had killed Faraday, Jensen and Ferrin. In it, the Zodiac included details about the murders that had not yet been released to the public, as well as a message to the police that when they cracked his code "they will have me".
On August 8, 1969, Donald and Bettye Harden of Salinas, California cracked the 408-symbol cryptogram. It contained a misspelled message in which the killer seemed to reference "The Most Dangerous Game". The author also said that he was collecting slaves for his afterlife. No name appears in this decoded text, and the killer said that he would not give away his identity because it would slow down or stop his slave collection.
On September 27, 1969, Pacific Union College students Bryan Hartnell and Cecelia Shepard were picnicking at Lake Berryessa on a small island connected by a sand spit to Twin Oak Ridge. A white man, about 5 feet 11 inches (1.80 m) weighing more than 170 pounds (77 kg), approached them wearing a black executioner's-type hood with clip-on sunglasses over the eye-holes and a bib-like device on his chest that had a white three-by-three-inch (7.6 cm × 7.6 cm) cross-circle symbol on it. He approached them with a gun, which Hartnell believed to be a .45. The hooded man claimed to be an escaped convict from a jail with a two-word name, in either Colorado or Montana (a police officer later inferred that the man had been referring to a jail in Deer Lodge, Montana), where he had killed a guard and subsequently stolen a car, explaining that he now needed their car and money to travel to Mexico because the vehicle that he had been driving was "too hot".
Two weeks later, on October 11, 1969, a white male passenger entered the cab driven by Paul Stine at the intersection of Mason and Geary Streets (one block west from Union Square) in San Francisco, requesting to be driven to Washington and Maple Streets in Presidio Heights. For reasons unknown, Stine drove one block past Maple to Cherry Street. The passenger then shot Stine once in the head with a 9 mm handgun, took Stine's wallet and car keys, and tore away a section of Stine's bloodstained shirt tail. The perpetrator was observed by three teenagers across the street at 9:55 p.m., and they phoned the police while the crime was in progress. They observed a man wiping the cab down before walking away toward the Presidio, one block to the north. Two blocks from the crime scene, patrol officers Don Fouke and Eric Zelms, responding to the call, observed a white man walking along the sidewalk east on Jackson Street and stepping onto a stairway leading up to the front yard of one of the homes on the north side of the street; the encounter lasted only five to ten seconds.
On October 14, 1969, the Chronicle received another letter from the Zodiac, this time containing a swatch of Paul Stine's shirt tail as proof he was the killer; it also included a threat about killing schoolchildren on a school bus. To do this, Zodiac wrote, "just shoot out the front tire & then pick off the kiddies as they come bouncing out". At 2:00 p.m. on October 20, 1969, someone claiming to be the Zodiac called the Oakland Police Department (OPD), demanding that one of two prominent lawyers, F. Lee Bailey or Melvin Belli, appear on A.M. San Francisco, a talk show on KGO-TV hosted by Jim Dunbar. Bailey was not available, but Belli did appear on the show. Dunbar appealed to the viewers to keep the lines open. Someone claiming to be the Zodiac called several times, and Belli asked the caller for a less ominous name and the caller picked "Sam". The caller said he would not reveal his true identity as he was afraid of being sent to the gas chamber (then California's capital punishment method). Belli arranged a rendezvous to meet the caller outside a shop on Mission Street in Daly City, but no one arrived. The call was later traced back to a patient in a mental institution, and investigators concluded that the man was not the Zodiac.
On November 8, 1969, the Zodiac mailed a card with another cryptogram consisting of 340 characters. This cipher, dubbed "Z-340", remained unsolved for over 51 years. On December 5, 2020, it was deciphered by an international team of private citizens, including American software engineer David Oranchak, Australian mathematician Sam Blake and Belgian programmer Jarl Van Eycke. In the decrypted message, the Zodiac denied being the "Sam" who spoke on A.M. San Francisco, explaining that he was not afraid of the gas chamber "because it will send me to paradice [sic] all the sooner". The team submitted their findings to the Federal Bureau of Investigation, which verified the discovery. The FBI stated that the decoded message gave no further clues to the identity of Zodiac.
Zodiac's letter sent to the San Francisco Chronicle on November 8, 1969 with the 340 Cipher, which was decrypted on December 5, 2020
On November 9, 1969, the Zodiac mailed a seven-page letter stating that two policemen stopped and actually spoke with him three minutes after he shot Stine. Excerpts from the letter were published in the Chronicle on November 12, including the Zodiac's claim; that same day, Officer Don Fouke wrote a memo explaining what had happened on the night of Stine's murder. On December 20, 1969, exactly one year after the murders of David Faraday and Betty Lou Jensen, the Zodiac mailed a letter to Belli that included another swatch of Stine's shirt; the Zodiac said that he wanted Belli to help him.
Zodiac continued to communicate with authorities for the remainder of 1970 via letters and greeting cards to the press. In a letter postmarked April 20, 1970, the Zodiac wrote, "My name is _____," followed by a 13-character cipher that hasn't been solved to this day. The Zodiac went on to state that he was not responsible for the recent bombing of a police station in San Francisco (referring to the February 18, 1970, death of Sgt. Brian McDonnell two days after the bombing at Park Station in Golden Gate Park) but added "there is more glory to killing a cop than a cid [sic] because a cop can shoot back." The letter included a diagram of a bomb the Zodiac claimed that he would use to blow up a school bus. At the bottom of the diagram, he wrote: " = 10, SFPD = 0."
On the night of March 22, 1970, Kathleen Johns was driving from San Bernardino to Petaluma to visit her mother. She was seven months pregnant and had her 10-month-old daughter beside her. While heading west on Highway 132 near Modesto, a car behind her began honking its horn and flashing its headlights. She pulled off the road and stopped. The man in the car parked behind her, approached her car, stated that he observed that her right rear wheel was wobbling, and offered to tighten the lug nuts. After finishing his work, the man drove off; yet when Johns pulled forward to re-enter the highway the wheel almost immediately came off the car. The man returned, offering to drive her to the nearest gas station for help. She and her daughter climbed into his car.
Zodiac's bomb schematic sent to the San Francisco Chronicle on April 20, 1970
Zodiac's letter sent to the San Francisco Chronicle on April 20, 1970
Zodiac sent a greeting card postmarked April 28, 1970 to the Chronicle. Written on the card was "I hope you enjoy yourselves when I have my BLAST," followed by the Zodiac's cross-circle signature. On the back of the card, the Zodiac threatened to use the bus bomb soon unless the newspaper published the full details that he had written. He also wanted to start seeing people wearing "some nice Zodiac butons [sic]".
In a letter postmarked June 26, 1970, the Zodiac stated that he was upset that he did not see people wearing Zodiac buttons. He wrote, "I shot a man sitting in a parked car with a .38." The Zodiac was possibly referring to the murder of 25-year-old Sgt. Richard Radetich one week earlier. At 5:25 a.m. on June 19, Radetich was writing a parking ticket in his squad car when an assailant unrelated to the traffic violation shot him in the head with a .38-caliber pistol through the closed driver's side window. Radetich died 15 hours later. The San Francisco Police Department (SFPD) denies that the Zodiac was involved; the murder remains unsolved.
In a letter to the Chronicle postmarked July 24, 1970, the Zodiac took credit for Kathleen Johns's abduction, four months after the incident. In a July 26, 1970 letter, the Zodiac paraphrased a song from The Mikado, adding his own lyrics about making a "little list" of the ways in which he planned to torture his "slaves" in "paradice [sic]". The letter was signed with a large, exaggerated crossed-circle symbol and a new score: " = 13, SFPD = 0". A final note at the bottom of the letter stated, "P.S. The Mt. Diablo code concerns Radians + # inches along the radians." In 1981, a close examination of the radian hint by Zodiac researcher Gareth Penn led to the discovery that a radian angle, when placed over the map per Zodiac's instructions, pointed to the locations of two Zodiac attacks.
Lass was a nurse at the Sahara Tahoe hotel and casino. She worked until about 2:00 a.m. on September 6, 1970, treating her last patient at 1:40 a.m. Later that same day, both Lass's employer and her landlord received phone calls from an unknown male falsely claiming that Lass had left town because of a family emergency. Lass was never found. What appeared to be a gravesite was discovered near the Clair Tappaan Lodge in Norden, California, on Sierra Club property. No evidence has been uncovered to definitively connect the Lass disappearance with the Zodiac Killer.
On March 22, 1971, a postcard to the Chronicle, addressed to "Paul Averly" [sic] and believed to be from the Zodiac, appeared to claim responsibility for the disappearance of Donna Lass on September 6, 1970. Made from a collage of advertisements and magazine lettering, it featured a scene from an advertisement for Forest Pines condominiums and the text "Sierra Club", "Sought Victim 12", "peek through the pines", "pass Lake Tahoe areas", and "around in the snow". The Zodiac's crossed-circle symbol was in both the place of the usual return address and the lower-right section of the front face of the postcard.
On October 7, 1970, the Chronicle received a three-by-five inch card signed by the Zodiac with the and a small cross reportedly drawn with blood. The card's message was formed by pasting words and letters from an edition of the Chronicle, and thirteen holes were punched across the card. Inspectors Armstrong and Toschi agreed that it was "highly probable" that the card had been sent by the Zodiac.
On October 27, 1970, Chronicle reporter Paul Avery (who had been covering the Zodiac case) received a Halloween card signed with a letter 'Z' and the Zodiac's crossed-circle symbol. Handwritten inside the card was the note "Peek-a-boo, you are doomed." The threat was taken seriously and was the subject of a front-page story in the Chronicle. Soon after receiving the letter, Avery received an anonymous letter alerting him to the similarities between the Zodiac's activities and the unsolved murder of Cheri Jo Bates, which had occurred four years earlier at the city college in Riverside in the Greater Los Angeles Area, more than 400 miles (640 km) south of San Francisco. Avery reported his findings in the Chronicle on November 16, 1970.
On March 13, 1971, five months after Avery's article linking the Zodiac to the Riverside murder, the Zodiac mailed a letter to the Los Angeles Times. In the letter he credited the police, instead of Avery, for discovering his "Riverside activity, but they are only finding the easy ones, there are a hell of a lot more down there".
In September 1972, San Francisco police obtained a search warrant for Allen's residence. In 1974, Allen was arrested for sexually assaulting a 12-year-old boy; he pleaded guilty and served two years imprisonment.
After the Lake Tahoe card, the Zodiac remained silent for nearly three years. The Chronicle then received a letter from the Zodiac, postmarked January 29, 1974, praising The Exorcist as "the best saterical comidy [sic] that I have ever seen". The letter included a snippet of verse from The Mikado and an unusual symbol at the bottom that has remained unexplained by researchers. Zodiac concluded the letter with a new score, "Me = 37, SFPD = 0".
Of further communications sent by the public to members of the news media, some contained similar characteristics of previous Zodiac writings. The Chronicle received a letter postmarked February 14, 1974, informing the editor that the initials for the Symbionese Liberation Army spelled out an Old Norse word meaning "kill". However, the handwriting was not authenticated as the Zodiac's.
A letter to the Chronicle, postmarked May 8, 1974, featured a complaint that the movie Badlands was "murder-glorification" and asked the paper to cut its advertisements. Signed only "A citizen", the handwriting, tone, and surface irony were all similar to earlier Zodiac communications. The Chronicle subsequently received an anonymous letter postmarked July 8, 1974, complaining of their publishing the writings of the antifeminist columnist Marco Spinelli. The letter was signed "the Red Phantom (red with rage)". The Zodiac's authorship of this letter is debated.
A letter, dated April 24, 1978, was initially deemed authentic but was declared a hoax less than three months later by three experts. Dave Toschi, the SFPD homicide detective who had worked the case since the Stine murder, was thought to have forged the letter. Author Armistead Maupin believed the letter to be similar to "fan mail" that praised the work of Toschi in the investigation, which he received in 1976; he believed both letters were written by Toschi. While he admitted to writing the fan mail, Toschi denied forging the Zodiac letter and was eventually cleared of any charges. The authenticity of this letter remains unverified.
After hearing the victims' screams for help, a man and his son who were fishing in a nearby cove discovered the victims and summoned help by contacting park rangers. Napa County Sheriff's deputies Dave Collins and Ray Land were the first law enforcement officers to arrive at the crime scene. Shepard was conscious when Collins arrived, providing him with a detailed description of the attacker. Hartnell and Shepard were taken to Queen of the Valley Hospital in Napa by ambulance. Shepard lapsed into a coma during transport and never regained consciousness. She died two days later, but Hartnell survived to recount his tale to the press. Napa County detective Ken Narlow, who was assigned to the case from the outset, worked on solving the crime until his retirement from the department in 1987.
Other evidence existed against Allen, albeit entirely circumstantial. A letter sent to the Riverside Police Department from Bates's killer was typed with a Royal typewriter with an Elite type, the same brand found during the February 1991 search of Allen's residence. He owned and wore a Zodiac brand wristwatch. He lived in Vallejo and worked minutes away from where one of the Zodiac victims (Ferrin) lived and from where one of the killings took place.
Robert Graysmith's book Zodiac advanced Arthur Leigh Allen, who died in 1992, as a potential suspect based on circumstantial evidence. Allen had been interviewed by police from the early days of the Zodiac investigations and was the subject of several search warrants over a 20-year period. In 2007, Graysmith noted that several police detectives described Allen as the most likely suspect. In 2010, Dave Toschi stated that all the evidence against Allen ultimately "turned out to be negative". Toschi's daughter said in 2018 that her father had always thought Allen had been the killer, but they did not have the evidence to prove it. Mark Ruffalo, who portrayed Toschi in the 2007 film Zodiac, commented, "If you get into who these cops were, you realize how they have to take their hunches, their personal beliefs, out of it. Dave Toschi said to me, 'As soon as that guy walked in the door, I knew it was him.' He was sure he had him, but he never had a solid piece of evidence. So he had to keep investigating every other lead."
The Zodiac originated the name himself in a series of taunting letters and cards that he mailed to regional newspapers, threatening killing sprees and bombings if they were not printed. Some of the letters included cryptograms, or ciphers, in which the killer claimed that he was collecting his victims as slaves for the afterlife. Of the four ciphers he produced, two remain unsolved, and one was only cracked in 2020. While many theories regarding the identity of the killer have been suggested, the only suspect authorities ever publicly named was Arthur Leigh Allen, a former elementary school teacher and convicted sex offender who died in 1992.
In 2002, the SFPD developed a partial DNA profile from the saliva on stamps and envelopes of Zodiac's letters. The SFPD compared this partial DNA to the DNA of Arthur Leigh Allen. A DNA comparison was also made with the DNA of Don Cheney, who was Allen's former close friend and the first person to suggest Allen may be the Zodiac Killer. Since neither test result indicated a match, Allen and Cheney were excluded as the contributors of the DNA.
Although the Zodiac ceased written communications around 1974, the unusual nature of the case led to international interest that has sustained throughout the years. The San Francisco Police Department marked the case "inactive" in April 2004, but re-opened it at some point prior to March 2007. The case also remains open in the city of Vallejo, as well as in Napa County and Solano County. The California Department of Justice has maintained an open case file on the Zodiac murders since 1969.
In April 2004, the SFPD marked the case "inactive", citing caseload pressure and resource demands, effectively closing the case. However, they re-opened their case sometime before March 2007. The case is open in Napa County and in the city of Riverside.
On March 3, 2007, an American Greetings Christmas card sent to the Chronicle, postmarked 1990 in Eureka, was re-discovered in their photo files by editorial assistant Daniel King. This letter was handed over to the Vallejo police. Inside the envelope, with the card, was a photocopy of two U.S. Postal keys on a magnet keychain. The handwriting on the envelope resembles Zodiac's print but was declared inauthentic by forensic document examiner Lloyd Cunningham; however, not all Zodiac experts agree with Cunningham's analysis. There is no return address on the envelope nor is his crossed-circle signature to be found. The card itself is unmarked. The Chronicle turned over all the material to the Vallejo Police Department for further analysis.
In October 2021, the Case Breakers, a team of over 40 cold case investigators composed of former law enforcement investigators, military intelligence officers, and journalists, claimed to have identified the Zodiac Killer as Gary Francis Poste, who died in 2018. The team claimed to have uncovered forensic evidence and photos from Poste's darkroom, and noted that scars on Poste's forehead matched those they said were described on the killer. They also claimed that removing the letters of Poste's name from one of Zodiac's cryptograms revealed an alternate message. The FBI subsequently stated that the case remained open and that there is "no new information to report," while local law enforcement expressed skepticism of the team's findings to the Chronicle. Riverside police officer Ryan Railsback said the Case Breakers' claims largely relied on circumstantial evidence, and author Tom Voigt, a Zodiac Killer investigator, called the claims "bullshit." Voigt noted that no witnesses in the case described Zodiac as having scars on his forehead.
In May 2018, the Vallejo Police Department announced their intention to attempt to collect the Zodiac Killer's DNA from the back of stamps he used during his correspondence. The analysis, by a private laboratory, was expected to check the DNA against GEDmatch. It was hoped the Zodiac Killer may be caught in a similar fashion to the "Golden State Killer" Joseph James DeAngelo. In May 2018, a Vallejo police detective said that results were expected in several weeks. However, as of June 2022, no results have been reported.
—The solution to Zodiac's 340-symbol cipher, solved in December 2020, including faithful transliterations of spelling and grammar errors in the original.