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.

One of the most prominent figures associated with the assassination of President John F. Kennedy has died: Clint Hill, the Secret Service agent who jumped onto the back of the limousine moments after shots rang out in Dealy Plaza. Those who knew him tell CBS News Texas that Hill never really overcame the guilt he felt on that tragic day.