SAN QUENTIN, Calif. (AP) — Serial killer Douglas Daniel Clark, who was sentenced to death for six grisly murders in California during the early 1980s, has died of natural causes, officials said Thursday. He was 75.

Clark, who’d been housed at San Quentin Rehabilitation Center, died Wednesday at an outside medical facility, according to a statement from the California Department of Corrections and Rehabilitation.

Clark and his accomplice Carol Bundy were dubbed the Sunset Strip Killers following a series of murders around Los Angeles starting in 1980. The victims included teenage girls and female sex workers.

Clark was convicted of multiple charges including murder, attempted murder and sexual contact with human remains.

The Marin County Coroner’s office will determine Clark’s official cause of death.

Bundy died at Central California Women’s Facility in 2003.