Private First Class Hearn was a member of the 19th Infantry Regiment, 24th Infantry Division. He was seriously injured in South Korea on 14 July 1950 and returned to duty on 31 July 1950. He was seriously wounded by the enemy in South Korea on 6 August 1950 and returned to duty on 30 August 1950. He was Killed in Action while fighting the enemy in South Korea on 23 September 1950.

Hearn was awarded 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.