During a firefight on that day, in Hậu Nghĩa Province, Republic of Vietnam during Operation Toan Thang III, Hartsock smothered an enemy satchel charge with his body to protect those around him and was mortally wounded in the explosion.

Staff Sergeant Hartsock's official Medal of Honor citation reads: For conspicuous gallantry and intrepidity in action at the risk of his life above and beyond the call of duty.

Realizing the enemy squad was heading for the brigade tactical operations center and nearby prisoner compound, they concealed themselves and, although heavily outnumbered, awaited the approach of the hostile soldiers.

Hartsock crawled about 5 meters to a ditch and provided heavy suppressive fire, completely pinning down the enemy and allowing his commander to seek shelter.

Hartsock's extraordinary heroism and profound concern for the lives of his fellow soldiers were in keeping with the highest traditions of the military service and reflect great credit on him, his unit, and the U.S. Army.