Death row inmate from Riverside County killed in prison attack; mob attacks suspect

A Riverside County death row inmate was allegedly killed by another prisoner at Kern Valley State Prison on Friday morning, June 6, sparking a violent mob assault involving more than 30 inmates, according to state prison officials.

Around 10:30 a.m., inmate Mario Renteria, 36, attacked Julian Mendez, 46, the California Department of Corrections and Rehabilitation said. Officials did not provide details of the attack beyond stating that he was “striking” Mendez, and it not clear what prompted the attack. However, an “improvised weapon” was later found at the scene.

The initial attack was halted, but moments later, a large group of inmates rushed Renteria and began assaulting him, the CDCR said. Despite repeated orders to stop, the group continued the attack until staff deployed multiple blast grenades to quell the violence.

Mendez was taken to the prison’s treatment center, where he was declared dead just after 11 a.m.

Mendez had been incarcerated at the prison since Dec. 2, 2004, after being sentenced to death in 2002 for the first-degree murder of two teenagers in Riverside County. The “Death Sentences Today” database, maintained by a professor at Drake University Law School, says Mendez committed the crime on Feb. 4, 2000, at age 22.

Renteria was admitted to state prison on April 27, 2022, also from Riverside County. He is serving a life sentence with the possibility of parole for first-degree murder — considered a third-strike offense — and arson. He has been moved to restricted housing pending the outcome of the investigation.

In the wake of the attacks, officials have limited movement within the prison to support the ongoing investigation.