The FBI verified 50 of the slayings that murderer Samuel Little confessed to, making him the most prolific serial killer in U.S. history. According to NBC News, the 79-year-old confessed to 93 murders between 1970 and 2005—admitting to murdering 90 victims as he was already serving three life sentences in California. The FBI said it was still attempting to confirm his other 40 confessions that have not been matched to cold cases. “For many years, Samuel Little believed he would not be caught because he thought no one was accounting for his victims,” Christie Palazzolo, an analyst for the FBI’s Violent Criminal Apprehension Program, said. “Even though he is already in prison, the FBI believes it is important to seek justice for each victim—to close every case possible.” Gary Ridgway, otherwise known as the Green River Killer, was convicted of 49 murders and confessed to about 20 more. Ted Bundy is thought to have killed more than 30. John Wayne Gacy is also thought to have killed more than 30 victims.