San Quentin inmate transferred from Southern California dies in suspected homicide

Officials at San Quentin State Penitentiary are investigating the death of a 70-year-old inmate in his cell as a homicide, the California Department of Corrections and Rehabilitation announced Wednesday.

The incident occurred around 3:30 p.m. on Sept. 17, according to a CDCR press release.

After an alarm was raised, prison staff went to the cell where the 70-year-old man, identified as Mark Squires, and his 36-year-old cellmate Gustavo Lopez were being held.

In the cell, they found Squires unconscious and immediately called 911 for medical help. In the meantime, they tried to save his life. They then took him to the prison triage unit, where they continued treatment.

Mark Squires, 70, and Gustavo Lopez, 36, appear in undated jail photos. (CDCR)

Medical staff at an outside prison pronounced Squires dead at 4:04 p.m.

“Lopez has been placed in restricted housing pending investigation by the SQRC Investigative Services Unit and the Marin County District Attorney’s Office,” the release said. “The Office of the Inspector General has been notified and the Marin County Coroner will determine the official cause of death for Squires.”

Lopez was transferred from Riverside County to San Quentin in January 2020 to serve 13 years and four months for kidnapping, bodily injury to a specified person resulting in a traumatic condition, and unlawful imprisonment by force.

Squires was also transferred from Riverside County, but in January 2000, and was serving a life sentence with the possibility of parole for lewd and lascivious acts with a child under the age of 14, involving force and failing to register as a sex offender.

Officials have not disclosed whether an inmate-made weapon was found.

No other injuries were reported to inmates or staff.

Opened in July 1852, San Quentin is California’s oldest prison. It houses more than 3,000 minimum, medium and maximum security inmates and employs nearly 1,800 people.