Captain Marr commanded Company I, 3rd Battalion, 31st Infantry Regiment, 7th Infantry Division. He was Killed in Action while fighting the enemy in North Korea on 3 December 1950. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

For his leadership and valor, Captain Marr was awarded the Silver Star Medal, the Bronze Star Medal, the Purple Heart with Oak Leaf Cluster, the Combat Infantryman 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.