Duncan joined the Army immediately after graduating from West High School in June 2006, and married his high school sweetheart Meaghun Valdez in October 2006 before being deployed to Iraq in January 2007. On Sept 4, 2007, he and four of his fellow soldiers were traveling in a convoy when their Humvee was hit by an explosively formed penetrator, a type of IED designed to explode on impact. Three of the soldiers perished, and Duncan and one other survived and eventually were taken to Brooke Army Medical Center in San Antonio, Texas. Duncan sustained quadruple amputations and burns over 50% of his body, and after five months of valiant efforts on the part of Duncan and his doctors, and with his wife and mother by his side, Duncan passed away one day before his 20th birthday.