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A Utah prison inmate has been charged with aggravated murder, accused of fatally assaulting his cellmate in August.

Julio Cesar Garza, 26, was charged last week in 6th District Court with the crime, which could carry the potential of the death penalty. Garza is accused of punching and kicking 24-year-old Carlos-Adrian Javier Hernandez inside their cell in the Gunnison prison facility on Aug. 25.

Hernandez had been serving a sentence of up to life for the 2007 murder and rape of 15-year-old Keely Amber Hall at a St. George park. He was 14 at the time of the murder.

Garza has been behind bars for aggravated robbery, possession of a prohibited item in a correctional facility and assault by a prisoner.

Video footage of their cell shows Garza punching into Hernandez's bunk, according to charging documents, then shows Garza pull Hernandez out of the bunk onto the floor before kicking and jumping on him during a minutes-long assault.

After several minutes, an alarm sounded and a corrections officer called a phone in the cell, according to charging documents. An inmate answered the phone, apologized for the alarm and said it wouldn't happen again, court documents state.

But the officer also heard "wheezing" in the background of the phone call, according to charges, and asked another officer to investigate.

That officer went to the cell and found Hernandez lying on the blood-covered floor, according to charges. Garza was not injured, the officer observed, but had blood spattered on his clothing. Hernandez was taken to a local hospital, where he died from his injuries.

The two had been cellmates for less than one day, investigators noted in court documents. No court dates had been set as of Thursday.