In 1968 and '69, the Zodiac Killer attacked seven people in four different Northern California locations. His first three targets were couples in secluded areas; two of these people survived. His last known victim was a taxi driver killed on October 11, 1969, in San Francisco. During and after his killing spree, Zodiac received attention and spread fear as he shared ciphers, letters, information and threats with authorities and the public. No murder has been officially linked to the Zodiac Killer since October 1969, but the unsolved case continues to fascinate.

[Watch The Hunt for the Zodiac Killer on A&E Crime Central.]

The Zodiac Killer murdered five people in under a year

Though the Zodiac Killer may also be responsible for other crimes, there are the five murders and two attempted murders officially attributed to him.

On December 20, 1968, in Benicia, California, 17-year-old David Faraday and 16-year-old Betty Lou Jensen were shot while parked on a lovers' lane during their first date.

Police initially had no idea a serial killer was responsible for these deaths. Therefore the investigation followed more standard steps, such as checking out Jensen's ex-boyfriend. Jensen's best friend later told SF Weekly, "All the detectives thought it had to be because of drugs. They refused to hear anything else."

Less than seven months later in the early morning hours of July 5, 1969, Darlene Ferrin, 22, and Mike Mageau, 19, were shot multiple times while sitting in Ferrin's car at the Blue Rock Springs Golf Club in Vallejo, California. Ferrin was killed, but Mageau survived the wounds to his jaw, shoulder and leg.

Less than an hour following the attack, Zodiac phoned the Vallejo police department to report the crime. During the call, he stated: "I also killed those kids last year," a reference to Faraday and Jensen.

On September 27, 1969, 22-year-old Cecilia Shepard and 20-year-old Bryan Hartnell were having a picnic at Lake Berryessa in Napa County. They were approached by a man wearing a hood that bore a symbol of two intersecting lines in a circle. The man used a gun to threaten Shepard and Hartnell, tied them up, then stabbed the pair.

Both Shepard and Hartnell were alive when help arrived. Shepard ended up succumbing to her wounds, but Hartnell recovered.

On October 11, 1969, in San Francisco, Zodiac entered the cab of Paul Stine, 29, as a passenger. While in the taxi, Zodiac shot Stine in the head.

Witnesses saw Stine's murder, so police were soon on the scene. The witnesses had described the murderer as white, around 25 to 30 years old, wearing glasses and sporting a crew cut. Police, who assumed the killing was a robbery, spotted a man matching this description — but a dispatcher had mistakenly told them the suspect was a Black person. The man was allowed to leave, and the Zodiac Killer was not caught.

Zodiac Killer Wanted poster
Wanted poster for the Zodiac Killer
Photo: Bettmann Archive/Getty Images

Zodiac would send letters to newspapers with cryptic clues

After his July 1969 attack, the Zodiac Killer began to contact newspapers via letters that included details only the killer would know. And in addition to phoning the police after the murders he committed in July, he made a phone call confession to law enforcement in September. The Zodiac Killer took responsibility for Stine's death in a letter postmarked October 13, 1969, enclosing a piece of the driver's bloodied shirt. He also reached out to the police by phone several days following that crime.

In a letter The San Francisco Examiner received on August 4, 1969, he wrote, "This is the Zodiac speaking," marking his first use of the name "Zodiac." That opening salutation would be repeated in many letters. His messages also often included a crosshairs symbol, which resembled the sight on a rifle — the same symbol on the hood worn during his September 1969 attack.

Zodiac seemed to enjoy the publicity he received. He took steps to ensure messages were widely shared, such as threatening to go on a "kill rampage" unless a cipher was printed in the San Francisco Chronicle, then issuing a separate threat to have a cipher published in The San Francisco Examiner. In a letter postmarked November 9, 1969, he taunted his pursuers, saying, "The police shall never catch me, because I have been too clever for them."

Of Zodiac's four coded messages, a married couple was able solve the first cipher to reveal that Zodiac had written, among other things, "I like killing people because it is so much fun." Zodiac claimed he'd shared his identity in another coded message. Yet despite decades of trying, no other Zodiac cipher has been officially solved.

Zodiac went silent for almost three years

The letter Zodiac sent taking responsibility for Stine's murder also declared, "School children make nice targets. I think I shall wipe out a school bus some morning. Just shoot out the front tire + then pick off the kiddies as they come bouncing out." The threat was published on October 17, 1969, and resulted in heightened fears and a greater police presence: officers guarded buses, helicopters kept watch from above and curfews were put into effect in several counties. Some parents opted to keep their children home from school entirely.

In 1969, Zodiac was consistently front-page news, while the knowledge that an unhinged serial killer was on the loose terrified the public. People rushed to call tip lines with the slightest information, overwhelming the police. Among letters that came in 1970 were threats to bomb a school bus and orders for residents of San Francisco to wear buttons with the crosshairs Zodiac symbol.

Zodiac letters and notes, including one declaring that each new victim meant "the more slaves I will collect for my afterlife," arrived until March 1971. Then Zodiac went silent until January 29, 1974, when he sent a new letter that noted, "Me – 37, SFPD – 0." This was seen as a claim he'd taken 37 lives. A few more letters and postcards arrived that year.

There was silence again until 1978 when a letter purportedly from Zodiac was sent to the San Francisco Chronicle. However, the legitimacy of the letter was questioned, as the handwriting and tone differed from earlier Zodiac communications. In addition, the discovery that year that a San Francisco detective had faked letters to the editor praising his own work on the case made some wonder if the detective had also falsified this Zodiac letter, something the detective and San Francisco police denied. The authenticity of the 1978 letter has not been confirmed.

There are theories that the Zodiac Killer eventually stopped killing

Though he'd claimed to be responsible for 37 deaths, no Zodiac victims have been discovered since 1969. Did he stop killing? Popular culture often depicts serial killers as operating under irresistible compulsions, but under certain circumstances, they can refrain from murder.

The FBI's National Center for the Analysis of Violent Crime has noted that serial killers may stop if something changes in their lives. Perhaps coming so close to getting caught on the night of Stine's murder scared Zodiac onto a safer path. Another possibility is that the terror he fomented in the public served as a substitute for killing. In addition, simply growing older may dampen predatory impulses.

A psychology professor who wrote a book about Zodiac has posited that the murderer may have recovered from dissociative identity disorder, otherwise known as multiple personalities. With recovery came an end to his desire to kill. It's also possible Zodiac stopped taking lives for a reason outside his control, such as institutionalization, incarceration or his own death.

Or perhaps Zodiac continued to hunt victims, but in a different way. A letter postmarked November 12, 1969, had threatened, "I shall no longer announce to anyone when I comitt my murders, they shall look like routine robberies, killings of anger, & few fake accidents, etc." Without knowing the killer, it's impossible to be certain whether his violence ceased.

Zodiac has never been identified

Both members of law enforcement and amateur sleuths continue to track the Zodiac Killer. Their work relies on the original investigations handled separately by law enforcement in Vallejo, Napa County and San Francisco. The case was not under federal jurisdiction, though the FBI provided support for analyzing handwriting, fingerprints and decoding Zodiac's messages.

Over the years, more than 2,500 suspects were considered, ranging as far afield as Unabomber Ted Kaczynski. A search warrant was executed for one prime suspect, Arthur Leigh Allen, but no definitive evidence was discovered. In addition, Allen's fingerprints did not match prints from Stine's taxi, and in 2002, DNA pulled from a Zodiac-sent stamp did not match Allen's. However, the DNA sample was small and the results somewhat inconclusive — plus Allen often had other people lick stamps for him.

Today's more advanced DNA techniques offer the tantalizing possibility of a definitive answer regarding who the Zodiac is, or was. But police in the 1960s and '70s had no idea that DNA analysis would arrive on the scene. Therefore some evidence was mishandled, or the chain of custody was broken. And pieces of evidence remain spread across various law enforcement agencies. In short, few things are available to analyze.

But in 2018, the Vallejo police department announced plans to submit some evidence in their possession for up-to-date DNA testing. A full DNA profile would make it possible to search open-source genealogy databases for a match. Another California killer, the Golden State Killer, was apprehended in 2018 thanks to this approach. But in the case of the Zodiac, no results have been reported thus far.

However, in 2020, three code breakers were able to solve one of Zodiac's ciphers, further providing evidence to help solve the identity of the killer.