A U.S. airman who helped disarm a gunman on a Paris-bound train last month will receive a Purple Heart medal, the U.S. Air Force leader said Monday, in an unusual award of the honor to a serviceman wounded while not in a combat zone.

Spencer Stone, 23, will receive the medal, which is given to troops wounded or killed in action against a U.S. enemy, U.S. Air Force Secretary Deborah James said in remarks at the Air Force Association Conference.

Stone, National Guardsman Alek Skarlatos and Anthony Sadler, a civilian, were vacationing in Europe last month when they saw a gunman on board a train from Amsterdam to Paris armed with a box cutter, a pistol, and a Kalashnikov AK-47 assault rifle.