By Faith Karimi
(CNN) -- Many have claimed to know the identity of the notorious Zodiac Killer, who terrorized northern California with a trail of unresolved murders in the 1960s. But their stories have not panned out.
Now, a Louisiana man believes he has the definitive answer to the chilling mystery: Who was the crazed, elusive killer who wrote letters bragging about his conquests?
Gary Stewart says it was Earl Van Best, Jr., his biological father, who died in 1984.
"I believe for the first time in the history of this case that I have presented more evidence that has ever been presented on any one suspect," Stewart told CNN's Erin Burnett about his new book.
The Zodiac Killer has been connected to five deaths between 1968-69. Though he was never caught, he gained notoriety by writing several letters to police and newspapers boasting of the slayings. He included swatches of bloody clothing as proof of his claims of killing as many as 37 people.
Stewart's quest for dad
Stewart was born in New Orleans, abandoned as a newborn in a stairwell in Baton Rouge, and later adopted.
About 10 years ago, when he was 39, his birth mother, Judy, contacted him for the first time. He then began his search for his biological father, whom both had not contacted since Stewart was abandoned.
The vice president of a cleaning company in the capital of Louisiana recounted his decade-long search for his biological father, which ended with the discovery that Best was the serial killer.
During the search, Stewart, who is married with a child, kept a journal that became the basis for the book, "The Most Dangerous Animal of All."
A chilling wanted poster
At one point during his search, he was watching television when a 1969 "Wanted" poster from the San Francisco Police Department flashed on the screen.
"And my heart stops. And I think I let out an audible scream, noise," he said.
His son rushed into the room, his eyes transfixed to the television.
"And he says hey, Dad, it's you. And I walked back to my office ... where I had the only photo I've ever had of my father, which I was told was an old DMV photo. But it turned out to be his 1962 mug shot for his rape of my mother. And I said, 'No, son, it's not me. It's my father.' "
Stewart said he reached his conclusion after years of research, including forensic experts comparing notes from the killer with his dad's handwriting on his marriage certificate. He said he also discovered his father's initials in cryptograms or ciphers the killer sent to newspapers.
"The Zodiac Killer insisted to the police ... if you crack the cipher, you'll have my identity," Stewart said.
They did, and they found the initials, but they still didn't know whom they belonged to, he said.
The San Francisco Police Department said it will investigate the revelation -- the latest person claiming links to the killer.
"It's an open and active case, so we don't comment," police spokesman Albie Esparza said this week.
"But (it's) certainly something our homicide investigators will take a look at."
Many past claims
Stewart is the latest in a series of people to make the claim that they descended from the famed Zodiac Killer.
There's the self-proclaimed "Stepson of the Zodiac Killer," Dennis Kaufman, who has appeared on TV news and a crime show touting his deceased stepfather Jack Tarrance as the crazed killer. He said his stepfather's handwriting was similar to the killer's.
There's Deborah Perez, who said she wrote some of the claims of responsibility for her father, Guy Ward Hendrickson, when she was 7 years old. Her half-sister called her claims lies.
There's Steve Hodel, who says his father was a columnist for the San Francisco Chronicle -- the paper to which the Zodiac Killer sent his mocking notes. His claim, too, was discounted.
Whether Stewart's contention will hold true is yet to be seen.
CNN's Michael Martinez contributed to this report.
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