A condemned inmate at Riverside County has reportedly been killed by another inmate within a state prison, prompting a violent response from fellow inmates on Friday morning, according to authorities.
The incident occurred at approximately 10:30 a.m. at Kern Valley State Prison, as reported by the California Department of Corrections and Rehabilitation (CDCR).
Investigators indicate that Mario Renteria, 36, allegedly initiated an attack on Julian Mendez, 46, the death row inmate. Specifics regarding the initial confrontation remain scarce; officials have not disclosed the exact nature of Renteria’s actions beyond describing them as “striking” Mendez, nor have they confirmed whether Mendez attempted to defend himself.
CDCR officials stated that staff instructed the inmates to “get down,” but the order was disregarded.
“Chemical agents were initially deployed to halt the assault; however, over 30 other inmates surged toward Renteria, attacking him,” noted the CDCR’s statement. “Despite repeated commands to cease, the violence persisted, necessitating the use of multiple blast grenades by staff to restore order.”
Once the disturbance was contained, authorities discovered Mendez with what was characterized as “multiple wounds,” prompting immediate life-saving efforts. An improvised weapon was also recovered from the scene.
Mendez was subsequently transported to the prison’s triage and treatment area, where medical personnel pronounced him dead at 11:05 a.m.
Julian Mendez (left) is depicted in a mugshot taken on May 14, 2024, while Mario Renteria (right) appears in a mugshot dated April 14, 2025. (CDCR)
Officials revealed that Mendez had been received from Riverside County on December 2, 2004, following his sentencing to death in 2002 for the first-degree murders of two teenagers.
As detailed on the “Death Sentences Today” website, maintained by a law professor at Drake University, Mendez committed these crimes on February 4, 2000, at the age of 22.
The website indicates that during his trial, the defense presented Mendez as a gang member who assaulted a 15-year-old boy, shooting him twice—once in the head—and subsequently ordered another gang member to execute a 14-year-old girl who witnessed the event.
“The other gang member declined to shoot [the girl], leading Mendez to ultimately take her life himself,” stated the site’s summary. “In mitigation, the defense contended that Mendez had spent much of his life involved in gang activity and that his father had been incarcerated for a significant portion of his life due to drug-related issues.”
In light of Mendez’s death, CDCR has placed Renteria in restricted housing while an investigation is underway. The department has also limited inmate movement to aid in this ongoing inquiry.
It was noted that Renteria was received from Riverside County on April 27, 2022, after being sentenced to life with the possibility of parole for first-degree murder (a third strike offense) and arson.
