LINCOLN, Neb. (AP) — A Nebraska prisoner already serving a life sentence for murder has been indicted on a new first-degree murder charge accusing him of killing his cellmate last year at the Nebraska State Penitentiary in Lincoln.

Angelo Bol, 31, was indicted this week in the November death of 20-year-old Kevin Carter, the Lincoln Journal Star reported. Authorities have not released details on how Carter was killed, saying only that staff members found him the evening of Nov. 6 unresponsive on his cell floor covered with a sheet.

Carter was serving a 6-to-9-year sentence for taking part in the beating and stabbing of a man in Douglas County in 2019. It wasn’t clear how Carter came to be placed in a cell with Bol, who is serving a life sentence for the 2014 shooting death a co-worker at a Gibbon meatpacking plant.

Carter’s death is the second in the recent years in which an inmate serving a life sentence is reported to have killed his cellmate in a Nebraska prison. In 2018, Patrick Schroeder was sentenced to death for strangling cellmate Terry Berry in the state prison at Tecumseh on April 15, 2017.

Berry, 22, was two weeks from his release when he died. Schroeder has said he warned guards he would kill Berry if prison authorities didn’t remove him from Schroeder’s cell.