SAN QUENTIN (CBS13) – A man on death row for killing three college students more than three decades ago has died of natural causes, according to prison officials.

The California Department of Corrections and Rehabilitation (CDCR) said Wednesday that 54-year-old David Leslie Murtishaw was found dead late Tuesday night in his cell at San Quentin State Prison. He was the only occupant of the cell.

Murtishaw was sentenced in 1978 in Kern County for murdering three University of Southern California students who were shooting a student film in the Mojave Desert. He has been on death row since 1979.

CDCR officials said since California reinstated the death penalty in 1978, 55 condemned inmates have died of natural causes, 19 have committed suicide, and 13 have been executed. 718 offenders remain on death row throughout the state.