54-year-old James Van Pelt died at a hospital outside the prison on Sunday. He was sentenced to death in 2002 for torturing and murdering a man in 1985.
There are currently 712-inmates on California's death row. Since 1978, 54 have died of natural causes. 13 have been executed.
At this point, it's unclear when executions will resume in the state. There hasn't been one in nearly five years.
Executions were blocked by a judge in 2006, after complaints about the administration of lethal injection in the gas chamber.