California Department of Corrections and Rehabilitation (CDCR) officials are actively investigating the death of an incarcerated individual, Julian Mendez, at Kern Valley State Prison (KVSP) on June 6, 2025, treating the case as a homicide. The incident has prompted a thorough inquiry by multiple agencies and led to restrictions within the facility.

The events reportedly began around 10:30 a.m. when incarcerated person Mario Renteria allegedly initiated an attack on Julian Mendez. Prison staff responded immediately, issuing orders for the men to cease their actions and get down. However, these commands were not heeded by the involved individuals.

According to official reports, chemical agents were deployed by staff, which initially appeared to stop the assault on Mendez by Renteria. However, the situation escalated rapidly when more than 30 other incarcerated individuals then rushed towards Renteria and began striking him. Staff once again issued orders to stop this subsequent violence, but these were ignored. To regain control and quell the widespread disturbance, staff resorted to using multiple blast grenades.

During the initial altercation allegedly initiated by Renteria, Julian Mendez sustained multiple wounds. Life-saving measures were immediately performed on Mendez, and he was transported to KVSP’s Triage and Treatment Area. Despite these efforts, a doctor pronounced Mendez deceased at 11:05 a.m. An improvised weapon was discovered at the scene of the incident.

Mario Renteria has since been placed in restricted housing as the investigation into Mendez's death continues. To facilitate the ongoing investigation, officials have limited population movement within the prison. The investigation is a collaborative effort involving KVSP’s Investigative Services Unit and the Kern County District Attorney’s Office.

The Office of the Inspector General has been notified of the incident. The Kern County Coroner's Office will be responsible for determining the official cause of Julian Mendez's death.

Julian Mendez, 46 years old at the time of his death, had been received by the CDCR from Riverside County on December 2, 2004. He was serving a condemned sentence issued in 2002 for the first-degree murder of two teenagers.

Mario Renteria, 36, was received by the CDCR from Riverside County on April 27, 2022. He was serving a sentence of life with the possibility of parole for first-degree murder, which was a third-strike offense, and an additional conviction for arson.

Kern Valley State Prison, which opened its doors in 2005, houses over 3,100 individuals in both minimum and high-security custody. The institution offers various academic classes and vocational programs and employs approximately 1,500 people.