Louisiana man Gary L. Stewart claims in a new book that during a search for his biological father he uncovered that he was the infamous Zodiac Killer that went on a killing spree in Northern California during the late 1960s.

Man Claims Dad Was Zodiac Killer

Stewart, who was adopted as a baby, claims in The Most Dangerous Animal of All: Searching for My Father … and Finding the Zodiac Killer that his curiosity was sparked about his father 10 years ago when his biological mother contacted him for the first time. Stewart's birth mother, Judy, hadn’t been in contact with the father since his birth, so it was up to Stewart to track him down.

Through his journey to find out more about his birth father, Earl Van Best Jr., Stewart came to the conclusion that he was the Zodiac Killer, the serial murderer who is thought to have killed five people between 1968 and 1969, and who claimed to have killed far more. He was notable during the late 60s for taunting police with boasts of his murders, sending them letters and pieces of bloody clothing.

"It's an open and active case, so we don't comment," San Francisco police spokesman Albie Esparza told CNN, referring to Stewart's findings. "But [it's] certainly something our homicide investigators will take a look at."

"We have talked to many people over the years,” added Napa County Sheriff’s Office’s Capt. Steve Blower. “We've gotten reports over the years from people who don't pan out. This case is still open, and we still do accept tips or leads that may have bearing on the case."

Among the evidence that Stewart provides in his book is a mugshot of the late Van Best (above), who had an extensive criminal record in San Francisco for forgeries. The mugshot image bears a striking resemblance to a police sketch purported to capture the likeness of the Zodiac killer.

"Stewart and [journalist Susan Mustafa] construct a chilling psychological profile of Stewart's father,” wrote the publisher of Stewart’s book. “As a boy with disturbing fixations, as a frustrated intellectual with pretensions to high culture, and as an inappropriate suitor and then jilted lover unable to process his rage,"

Zodiac, the 2007 feature film starring Jake Gyllenhaal, Mark Ruffalo and Robert Downey Jr., told the story of the San Francisco cartoonist that helped investigators try to nab the Zodiac Killer.