Private First Class Castillo, nicknamed "Chicko" was a member of Company L, 3rd Battalion, 21st Infantry Regiment, 24th Infantry Division. He was Killed in Action while fighting the enemy in North Korea on 11 April 1951.

Castillo 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.