LINCOLN, Neb. (AP) — Officials say an inmate at the Nebraska State Penitentiary died last month.

52-year-old John Loeffler died April 22 at a Lincoln hospital.

A news release posted on the Department of Correctional Services’ website five days after his death says he was taken to the hospital after being found unresponsive in his cell on April 20.

Loeffler had been in prison since 1992 after being convicted of robbery and use of a firearm to commit a felony in Douglas County. He had a tentative release date of Dec. 15, 2016.

A grand jury will investigate the death, as is required when someone dies in custody.