City prosecutors charged a 22-year-old prison detainee with first-degree murder in the beating death of another inmate at Oahu Community Correctional Center on Saturday.

Joseph Tui Jr. will make his initial appearance in District Court at 8:30 a.m. today. His bail was set at $250,000.

The Medical Examiner’s Office said the 76-year-old victim, whose name is being withheld until his relatives are informed of his death, died of head injuries caused by “blunt force trauma.”

The death was ruled a homicide.

The fight took place at 2 p.m. Saturday.

At the time of incident, Tui was being held on a third-degree assault charge.

The Department of Public Safety is investigating the cause of the fight, which happened during a shift change.

The two were housed in a holding unit for inmates who misbehave. They were sharing a cell because the facility is overcrowded, said Ted Sakai, director of public safety.

Tui was moved to the holding unit Thursday for threatening a staff member. The older inmate was in the unit for cigarette possession. He died at 4:12 p.m. Saturday after being taken to the hospital with head injuries.

Tui has a long record of convictions starting in 2000 for theft, burglary, escape, misdemeanor sex assault and harassment.

Four years ago he was assaulted by three adult corrections officer at Halawa Correctional Facility. The attack, caught on surveillance tape, led to the dismissal of the three guards.