Until now, HarperCollins kept secret a book written by a man who claims the Zodiac Killer is his father.

"The Most Dangerous Animal of All," written by Gary L. Stewart was published today (May 13), almost a year after the publishing house had gained access to the book. Currently, the book's Amazon sales rank at #140,113.

Stewart, a Louisiana resident who wrote the book with veteran crime genre journalist Susan Mustafa, spent 12 years researching the book, the publishing house's publicist told New York Magazine.

The 367 pages book documents Stewart's journey to find his biological father only to discover that his father was a criminal. The killer is connected to at least five murders, including attacks on multiple young couples, during 1968 and '69. The mass murderer taunted police and local media, sending clues in coded letters frequently to Bay Area newspapers.

Many people have come forward in the past claiming they knew who the killer was but all leads led to a cold path and the police were never able to arrest him.

If you look at Gary's photo next to the sketch of the Zodiac next to his father's mug shot, you can see that there is very clearly more than just a passing resemblance. They look alike," Tina Andreadis from the publishing house told the magazine.

"He didn't want to believe," she added. "I don't think most people want to know that their father is a notorious serial killer."

According to NY Times, the police received about 2,500 tips of the killer since the first crime took place. The unsolved case was the subject of the 2007 movie, "Zodiac."