(CNN) A convicted serial killer, who murdered and preyed on women in California over a span of three decades, died over the weekend at San Quentin State Prison.

Lonnie Franklin, known as the "Grim Sleeper," was found unresponsive in his cell Saturday night, according to a statement from the California Department of Corrections and Rehabilitation.

An autopsy is being performed to determine the 67-year-old's cause of death, but there were no signs of trauma, the statement said.

He was a former city trash collector and also worked as a garage attendant at a LAPD station.

Police collected DNA from some of the crime scenes but were unable to find a match for several years.

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