Second Lieutenant Umbarger was the pilot of a F-84E Thunderjet fighter with the 9th Fighter-Bomber Squadron, 49th Fighter-Bomber Wing. On 28 February 1952, while on a combat mission, his aircraft received a direct hit by anti-aircraft fire. His bailout was unsuccessful. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Umbarger was awarded the Air Medal, the Purple Heart, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.