SAN QUENTIN (CBS SF) – A condemned serial killer who murdered five Alameda County women after brutally beating and raping four of them has been found dead in his cell on San Quentin’s Death Row, prison officials announced Friday.

A former Navy sailor, 65-year-old Anthony McKnight was already serving a 63-year state prison sentence for attempted murder, rape and kidnapping of three women in 1987 when a series of DNA tests run in 1996 linked him to 1985 murders.

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anthony mcknight dept of corrections

Anthony McKnight (CDCR)

At the time of the 1985 murders, McKnight was stationed with the Navy on Treasure Island.

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After a nearly two-month-long trial in 2008 he was found guilty of the slayings and sentenced to die for the murders of Betty Stuart, 22; Diane Stone; 17; Talita Dixon, 13; Monique Davis, 18; and Beverly Bryant, 24.

Prison officials said McKnight was found unresponsive in his cell at 9:30 p.m. Thursday and was pronounced dead at 10:09 p.m. His cause of death is pending the results of an autopsy.

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Since 1978, when California reinstated capital punishment, 82 condemned inmates have died from natural causes, 27 have committed suicide, 13 have been executed in California, one was executed in Missouri, one was executed in Virginia, 14 have died from other causes and two – including McKnight – are pending a cause of death. There are currently 731 offenders on California’s death row.