A Secret Service agent who tried to shield former President John F. Kennedy from an assassin’s gunfire in 1963 died on Monday. Clint Hill, 93, died at his California home from unknown causes. He had been serving on presidential security detail for just three years when he made the move that defined his career.

Clint Hill, the former Secret Service agent who shielded first lady Jacqueline Kennedy from gunfire during the assassination of President John F. Kennedy in 1963, has died, the agency said Monday.