Police say a Northern Ireland prison officer targeted by an Irish Republican Army booby-trap bomb has died of a heart attack.

Adrian Ismay was wounded March 4 when a bomb beneath his van exploded in Belfast as he drove to work.

Chief Constable George Hamilton said 52-year-old Ismay died of a heart attack Tuesday, but police hadn't determined whether his bomb wounds contributed. Hamilton said it was too soon to say whether an IRA suspect charged with his attempted murder would have that charge raised to murder. He had been sent home from the hospital over the weekend, but was back in the hospital Tuesday.

While the dominant Provisional IRA renounced violence in 2005, breakaway groups remain active. The New IRA faction has claimed responsibility for the March 4 attack.