San Quentin inmate transferred from Southern California dies in possible homicide

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

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

In response to an alarm, prison staff approached a cell occupied by the 70-year-old, identified as Mark Squires, and his 36-year-old cellmate, Gustavo Lopez.

Inside the cell, they found Squires unresponsive and immediately called 911 for medical assistance while attempting life-saving measures on him before taking him to the prison’s triage area where treatment continued.

Medical personnel from an out-of-prison facility pronounced Squires dead at 4:04 p.m.

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

Lopez was transferred to San Quentin from Riverside County in January 2020 to serve 13 years and four months for kidnapping, corporal injury on a specific person resulting in traumatic condition and false imprisonment with violence.

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

Officials did not say if an inmate-manufactured weapon was recovered.

No other injuries to inmates or staff were reported.

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

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