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A Utah State Prison inmate who was already serving time for a homicide has pleaded guilty to killing his cellmate.

Mario Alfonso Lucero, also known as Mario Antoine Lucero, was charged in 3rd District Court with first-degree felony murder in the February 10 strangulation death of his cellmate, 23-year-old Julio Guerrero.

Lucero last month pleaded guilty to second-degree felony manslaughter, admitting he killed Guerrero during a fight.

Judge Mark Kouris immediately sentenced Lucero to a one-to-15-year prison term.

The judge ordered the new term to run concurrently with the one to 15 years Lucero was serving for beating a man to death in 2013 in St. George.

The prison slaying occurred a day after Lucero, 34, had moved into Guerrero's cell, charges state.

After another inmate reported there was "an issue" in Guerrero's cell, prison officials found Guerrero dead inside, according to charges.

Lucero was found to have suffered minor injuries.

An autopsy revealed that Guerrero died from "blunt force trauma" to his neck that caused asphyxia, according to charges.

Guerrero was in prison for parole violation, following about three years in prison for a 2010 robbery.