(AP) — A Nebraska prison inmate who assaulted a correctional officer earlier this month while being treated at a hospital has died.

The Nebraska Correctional Services Department says Robert Carter had been dealing with significant long-term health problems before he died Tuesday.

The 50-year-old was serving a 30-year sentence for several counts of robbery and for assaulting an officer. He wasn’t projected to be released until 2036.

Officials say Carter stabbed a correctional officer with a butter knife when he was being treated at a Lincoln hospital on Sept. 5.

Carter, who was from the Omaha area, was in the prison’s nursing care unit when he died.

A grand jury will investigate the death because Carter was in state custody.