Private First Class DeMaio was a Browning Automatic Rifleman with the 14th Infantry Regiment, 25th Infantry Division. He had volunteered to serve with an infantry company after assignment to regimental headquarters. He was Killed in Action while fighting the enemy on the "Jamestown Line" in North Korea on 5 January 1953.

DeMaio 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.