San Quentin officials investigate inmate’s possible homicide

The death of a prisoner at the San Quentin Rehabilitation Center on Tuesday is being investigating as a possible homicide, authorities said.

Around 3:30 p.m., Mark Squires, 70, was found unconscious in his cell. The staff called for emergency medical assistance. Squires was pronounced dead at 4:04 p.m., the prisons department reported.

Investigators placed Squires’ cellmate Gustavo Lopez, 36, into restricted housing. The prison’s investigation unit and the Marin County District Attorney’s Office will review the incident. Squires’ cause of death will be determined by the Marin County coroner’s office.

Squires was serving a life sentence with the possibility of parole for performing lewd or lascivious acts with a child under age 14 with violence, and failing to register as a sex offender. He was convicted in Riverside County.

The prison staff reported that Lopez is serving a 13-year sentence for kidnapping, corporal injury, and false imprisonment charges. Lopez also was convicted in Riverside County.