Corporal Killingsworth was a member of Headquarters Company, 1st Battalion, 38th Infantry Regiment, 2nd Infantry Division. He was Killed in Action while fighting the enemy near Hoengsong, South Korea on 12 February 1951. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Killingsworth was awarded the Purple Heart, the Combat Infantryman's Badge, 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.