(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. 
How many people did he definitely kill?
 37