FILE PHOTO: Condemned inmate Lawrence Sigmond Bittaker, who was sentenced to death in 1981 for the murder of five teenage girls, is seen in a handout picture taken August 24, 2018 and provided by California Department of Corrections and Rehabilitation on December 16, 2019. California Department of Corrections and Rehabilitation/Handout via REUTERS

(Reuters) - Lawrence Bittaker, one of two men who became known as the “Tool-Box Killers” for the torture, rape and murder of five teenage girls in 1979, has died of natural causes in a California prison, state officials said on Monday.

Bittaker, who was sentenced to death in 1981, died at the age of 79 at San Quentin State Prison on Friday, the California Department of Corrections said. An autopsy was pending.

Although there are 729 condemned inmates on California’s death row, the state has not executed a prisoner since 2006, when a federal judge declared its lethal injection protocol unconstitutional. In March, Governor Gavin Newsom signed an executive order suspending executions, saying he was deeply troubled by the possibility that an innocent person could be put to death.

Bittaker and Roy Lewis Norris, who met in prison, became known as the “Tool-Box Killers” because they used hammers and pliers to inflict pain on their victims before stabbing or strangling them.

Bittaker and Norris were arrested in November 1979 after being identified by a young woman who had survived the summertime attack.

Norris pleaded guilty to four counts of first-degree murder and one count of second-degree murder, testifying against Bittaker at a three-week trial. Norris was sentenced to 45 years to life and remains incarcerated, now 71 years old.

A Los Angeles Superior Court jury found Bittaker guilty of murder, kidnapping, rape and other charges and recommended that he be put to death.

Since 1978, when California reinstated capital punishment after a halt ordered by the U.S. Supreme Court, 82 condemned inmates have died from natural causes, 27 died by suicide and 13 have been executed. Two others were put to death in other states and 18 died of other causes.