The San Francisco Bay Area murderer in the late 1960s known as the Zodiac Killer may have finally been identified.

The mystery man responsible for killing at least five people is believed to be a 91-year-old man living in Solano County, Calif., according to a new book, The Zodiac Killer Cover-Up. Author Lyndon Lafferty, a childhood friend of the main suspect, reveals new theories.

The crimes happened four decades ago, but the identity of the Zodiac Killer has remained a mystery. Even though police formally closed the case in 2004, Lafferty, a former California Highway Patrol officer, hopes to shed some new light on the gruesome murders that struck Northern California.

According to Lafferty, the Zodiac Killer is a now 91 years old and lives in Solano County. While the book fails to reveal his name, Lafferty claims that the police investigated him as a suspect in the early 1970s. Power brokers caused the killer to be overlooked, reports the Los Angeles Times.

Lafferty knows that many people have admitted to being the Zodiac Killer, but as he told the San Francisco Chronicle last year, I feel that we have a very credible case.

The Zodiac Killer's confirmed victims were 17-year-old David Farrady, 16-year-old Betty Lou Jensen, 22-year-old Darlene Ferrin, 22-year-old Cecilia Shephard and 29-year-old Paul Stine. The five murders occurred between December 1968 and October 1969. He was suspected of many more slayings, and two people managed to survive the Zodiac Killer's attacks.

The killer would send letters embedded with clues, but they were so complicated that police struggled to solve them.

According to the Daily Mail, police reopened the case in 2007, with DNA evidence clearing their main suspect, Arthur Leigh Allen.

Lafferty, who also happened to have been Allen's high school classmate, believes that police have known the identity of the real Zodiac Killer since March 15, 1971.

One claim of Lafferty's, reported by the Daily Republic, is that the Zodiac Killer was motivated to kill because of jealousy stemming from his wife's affair with a Solano County Superior Court Judge.

Mind and body ravaged by years of severe alcoholism, his blood-lusting revenge turned him into the most shocking and vicious killer in our 20th century, Lafferty wrote in The Zodiac Killer Cover-Up. Through his taunting of the police, his codes, ciphers, and letters, he was on a mission to redeem his shattered ego, to prove that he is better, smarter, and more clever than all the judges and police put together.

Lafferty's obsession with the case began when he saw a suspicious man parked at rest stops in the 70s. According to the author, the man resembled the wanted posters of the killer.

The book is now being published because Lafferty said that he had to wait until some people, including the suspect's wife, finally died.

Lafferty isn't the only person to suspect the 91-year-old California man. After showing a picture of the suspect to Pam Huckaby, the sister of the Zodiac Killer's third victim, Darlene Ferrin, Huckaby reportedly answered, It's him.