The | Most Dangerous Animal Of All

After being contacted by his birth mother at age 39, Stewart began investigating his biological father, . Stewart claims that Van Best Jr. is the Zodiac Killer based on several pieces of circumstantial evidence:

Van Best Jr. was a convicted pedophile with a history of predatory behavior, providing a psychological profile that Stewart argued fit the killer. The FX Docuseries and Debunking The Most Dangerous Animal of All

Stewart claimed to find his father's name, "Earl Van Best Jr.," hidden within the Zodiac’s famous unsolved cryptograms. After being contacted by his birth mother at

is a New York Times bestselling true-crime memoir by Gary L. Stewart and Susan Mustafa that presents a theory identifying the infamous Zodiac Killer . Published in 2014, the book chronicles Stewart's decade-long search for his biological father, which ultimately led him to believe his father was the elusive serial murderer. Core Premise and Theory was a convicted pedophile with a history of

Stewart noted a striking similarity between his father's mugshot and the 1969 police sketch of the Zodiac.

A handwriting expert initially suggested that Van Best Jr.'s writing on a marriage certificate matched the Zodiac's cryptic letters.