Lieutenant Gergen was the pilot of a F4U-4B Corsair fighter with Fighter Squadron 53, aboard the aircraft carrier USS Essex (CV-9). On 21 February 1952, he was escorting a flak damaged aircraft to Sokcho-ri Airfield (K-50), North Korea through a snow storm, when he became disoriented and his aircraft suddenly swerved and crashed into the sea. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

For his leadership and valor, Lieutenant Gergen was awarded the Distinguished Flying Cross, the Air Medal with 2 Gold Stars, the Purple Heart, the Commendation Ribbon, the Combat Action Ribbon, 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.