(KTXL) — A Southern California man was killed while serving time at a prison in Amador County, state prison officials said. 

The California Department of Corrections and Rehabilitation said Mule Creek State Prison staff found 23-year-old Robert Aranda injured inside his cell on Feb. 2, around 1:40 p.m. 

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Aranda reportedly had several stab wounds and was pronounced dead less than an hour later. Prison staff identified the suspect in Aranda’s killing as 38-year-old Alexander Mateuz, his cellmate. 

The CDCR said an investigation is being conducted, and Mateuz has been moved to a separate unit in the meantime.

According to the CDCR, Mateuz is serving life with parole. 

He was convicted in August of 2008 for assault with a firearm as a third-striker, use of a firearm and an enhancement of a street gang act in the commission of a violent felony.

Aranda was convicted in November of 2021 and was serving a 13-year sentence for two counts of second-degree attempted murder with the use of a firearm.

His next of kin has been notified.