Denied status as a conscientious objector, Kays fled to Canada to avoid getting drafted for military service in Vietnam until the US Army guaranteed he would be able to serve as a medic.

During a firefight on that day, in Thừa Thiên–Huế Province, Republic of Vietnam, Kays repeatedly exposed himself to enemy fire in order to treat wounded soldiers, even after losing his lower left leg to an explosion.

After returning to Illinois, Kays went on to struggle with drug addiction and mental health issues, due to the post-traumatic stress disorder that came from his service during the war.

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

A heavily armed force of enemy sappers and infantrymen assaulted Company D's night defensive position, wounding and killing a number of its members.

Kays resumed his heroic lifesaving efforts by moving beyond the company's perimeter into enemy held territory to treat a wounded American lying there.