(WASHINGTON) — The U.S. military believes someone in a Niger village may have tipped off attackers to the presence of U.S. commandoes and Nigerien forces in the area, setting in motion the ambush that killed four Americans, a senior defense official said Tuesday. The official said the Army Green Berets and about 30 Niger forces stopped in a village for an hour or two to get food and water after conducting an overnight reconnaissance mission.