Sergeant First Class Theriault was a medic with the Medical Company, 21st Infantry Regiment, 24th Infantry Division. He was reported as Missing in Action while tending his wounded comrades in South Korea on 4 September 1950. He was presumed dead on 31 December 1953. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

For his leadership and valor, Sergeant First Class Theriault was awarded the Bronze Star Medal with Oak Leaf Cluster, the Purple Heart with Oak Leaf Cluster, the Combat Medical 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.