Samuel Little, the man the FBI has called the most prolific serial killer in the history of the United States, died Wednesday at age 80, a law enforcement source confirmed to "60 Minutes." The cause of death has not yet been determined.

The California Department of Corrections and Rehabilitation confirmed Little's death later Wednesday in a press release.

Little, who in 2018 confessed to 93 murders over more than three decades, had been in jail since 2014 for the murders of three women he strangled. He confessed to the other murders under questioning by Ranger James Holland – the story of those confessions was told by "60 Minutes" in October 2019.