Inmate imprisoned for murder is beaten and killed by other inmates at California prison

LOS ANGELES — A convicted murderer was killed this week in an assault by other inmates at a Southern California prison, authorities said.

Staff at Calipatria State Prison in Imperial County witnessed the beating death of Alberto Martinez, 46, in the prison yard on Thursday, authorities said.

Inmate Tyler A. Lua struck him, knocked him to the ground and continued to hit him, the California Department of Corrections and Rehabilitation said in a news release.

Two other inmates, Jorge D. Negrete-Larios and Luis J. Beltran, began hitting Martinez as he lay motionless, and staff "stopped the incident using pepper spray and one baton strike," the department said.

The department said Martinez had "injuries consistent with an incarcerated-manufactured weapon," and two such weapons were found where the attack occurred.

Medical staff attempted to treat Martinez's injuries, but he died within an hour. Prison officials say they are investigating his death as a homicide.

The Imperial County Coroner will determine the exact cause of death.

Martinez had been sentenced to death in 2010 after being convicted of first-degree murder for his role in abducting and killing a man in exchange for payment from the man's sister.

Martinez described himself in court as an associate of the Mexican Mafia. He was featured in a 2023 Los Angeles Times article detailing how members of the prison-based crime syndicate use smuggled cellphones to collect money and order murders on city streets.

Although Martinez was initially on death row, he was among the condemned prisoners who were moved to the general population after Gov. Gavin Newsom imposed a moratorium on executions in 2019.

According to the Department of Corrections, Martinez was also serving a life sentence for attempted first-degree murder, as well as another two-year sentence for street gang activity.

The three inmates who were involved were "placed in restricted housing" pending an investigation, the department said.

Lua and Negrete-Larios are both serving sentences for attempted second-degree murder and other convictions. Beltran was sentenced in 2023 to life in prison for first-degree murder.