Inmate Steven Brenneman, 40, was found unresponsive in his cell Monday and later pronounced dead at Delano Regional Medical Center. Brenneman died from blunt-force trauma to the head, according to prison officials.
Brenneman's cellmate, 40-year-old Walter Tamayo, is suspected in the killing and has been placed in a segregated unit during the investigation, according to prison officials.
Brenneman was serving an 18-year sentence from Riverside County for rape with force and violence and penetration with a foreign object.
Tamayo is serving a life sentence from Los Angeles County for first-degree murder and attempted first-degree murder.