First Lieutenant Pentecost was the pilot of a F-84E Thunderjet fighter with the 428th Fighter Bomber Squadron, 474th Fighter Bomber Group. On January 13, 1953, while on a combat mission, his aircraft received a direct hit by anti-aircraft fire, its right wing fell off and it crashed into the water. He was presumed dead on February 3, 1953. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.