A pair of Apaches were flying together, and one of them took the shot, the official said.
There was no immediate word how many ISIS fighters were killed in the U.S. strike.
The U.S. attack happened near the Iraqi city of Qayyarah, roughly 50 miles south of Mosul, Iraq’s second largest city and an ISIS stronghold where the majority of ISIS fighters reside inside Iraq, according to defense officials.
Mosul fell to ISIS two years ago in June 2014.