A death row inmate was beaten to death by three other inmates at a prison in Southern California, according to officials.

Alberto Martinez was killed in the Calipatria State Prison in Imperial County on Thursday, the California Department of Corrections and Rehabilitation said in a news release. His death is being investigated as a homicide.

Another inmate, Tyler A. Lua, was observed by prison staff striking Martinez and knocking him to the ground before he continued to hit him. Lue eventually stepped away from Martinez, but two other inmates — Jorge D. Negrete-Larios and Luis J. Beltran — began striking Martinez as he laid motionless on the ground.

Staff then stopped the beating using pepper spray and a baton strike. Two incarcerated-manufactured weapons were found at the scene.

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Martinez sustained injuries consistent with an incarcerated-manufactured weapon. No staff or other inmates were injured.

Emergency responders were called to the scene and medical staff performed life-saving measures on Martinez. He was transported to the prison’s treatment area and was pronounced dead at 2:20 p.m.

Movement has been limited in the yard where the alleged attack happened.

Lua, Negrete-Larios and Beltran were moved to restricted housing pending an investigation into the incident.

Martinez, 46, was most recently received from Orange County on Aug. 17, 2010, and placed on condemned status for first-degree murder. He was also sentenced to life with the possibility of parole for attempted first-degree murder with an enhancement for street gang activity and two years for street gang activity, a sentence that was to be served concurrently with the condemned sentence.

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He acted as the getaway driver in a botched plot to kidnap and murder a businessman, according to the Orange County Register. The plot was reportedly orchestrated by the businessman’s sister.

According to the Los Angeles Times, Martinez was a powerful member of a Mexican mafia who orchestrated murders while on death row and communicated with a woman from Mexico using a cellphone he was prohibited from having.

Lua, 25, was received from San Bernardino County on Jan. 31, 2019, and sentenced to 19 years in prison for attempted second-degree murder with an enhancement for use of a firearm. During his incarceration, he was sentenced to two additional years for having a controlled substance in prison.

Negrete-Larios, 33, was received from Riverside County on July 5, 2016, and sentenced to 32 years and four months in prison for attempted second-degree murder with enhancements for inflicting great bodily injury, discharge of a firearm and street gang activity in commission of a violent felony.

Beltran, 31, was received from Los Angeles County on April 6, 2023, and sentenced to life in prison without parole for first-degree murder with enhancements for intentional discharge of a firearm causing great bodily injury or death and possession of a firearm as a felon.

There are a total of 623 inmates with condemned sentences in California prisons, according to the state’s Department of Corrections and Rehabilitation.

In 2019, California Gov. Gavin Newsom, a Democrat, signed an executive order that instituted a moratorium on the death penalty in the Golden State. The order also called for the repeal of the state’s lethal injection protocol and the immediate closing of the state’s execution chamber at San Quentin State Prison.

The last execution in California was carried out in 2006.