Gary Stewart wasn’t thrilled when he found out that the father he never knew was the infamous Zodiac Killer, but he’s set to make a nice profit out of it with the publication of his new book, The Most Dangerous Animal of All. In his 12-year-search, Stewart spoke to handwriting specialists, forensic scientists and over 500 people, all with the hope of finding out more about the man, who he thinks is his biological father.

The Zodiac killer terrorized Northern California in the 1960s and is believed to be responsible for five mysterious deaths. The identity of the killer was never discovered and the Zodiac killer has gone on to fascinate and puzzle many mystery hunters since then.

Jake Gyllenhaal
Jake Gyllenhaal starred in the 2007 movie based on the Zodiac case.

Most recently, the killer’s crime spree was the focal point of the 2007 film Zodiac, starring Jake Gyllenhaal. In it, Gyllenhaal plays a San Francisco detective, who, much like Stewart, develops an obsession with the killer. The David Fincher-directed flick got a lot of love from critics. It holds an 89% “Fresh” rating on review aggregator Rotten Tomatoes. On its release, Roger Ebert gave the film five stars, with Empire Magazine’s review describing it as “Beautifully poised, slow and sinister: a trance of expectant menace.”

Read Sean Cornell's review for Contactmusic here.

As for Stewart, he hopes that the book can do more than satisfy the public’s morbid fascination with the Zodiac Killer.

"I'm really hoping this will bring some closure to the families of my father's victims," he said about the product of his decade-long search.