“I want to be the best serial killer out there,” Gary Ridgway confesses in Investigation Discovery’s two-hour special The Green River Killer: Mind of a Monster. “I was just going for the count.” When the Green River Killer finally talked with police he said he wanted to kill as many prostitutes as possible. He figured sex workers wouldn’t be reported missing and he, a god-fearing man, hated them.

“Beginning in the early 1980s, Washington state was gripped with fear as the bodies of young women began appearing along the banks of the Green River,” reads the ID press statement. “As the number of victims grew, investigators created a taskforce and enlisted the help of the FBI, but it took almost 20 years to finally catch their man.”

Young runaways and prostitutes began disappearing from state Route 99 in south King County, Washington in 1982. Ridgway prowled the Pacific Highway South for transient women, often teens. He brought many of the victims to his home where he strangled them before dumping the bodies in remote sites along the Green River, which is how he got his name.

The special uses in-depth interviews from investigators who worked the case, along with footage. The Green River Killer: Mind of a Monster also reveals, in Ridgway’s own words, how his troubling behavior as a child morphed into murder. “The confessions expose the truths behind a violent predator with complete disregard for human life,” Henry Schleiff, Group President of Investigation Discovery, Travel Channel, American Heroes Channel and Destination America, said in a statement.