NOGALES, Ariz. (AP) — A pair of Mexican drug smugglers in camouflage pants, bundles of marijuana strapped to their backs, scaled a 25 foot-high fence in the middle of the night, slipped quietly into the United States and dashed into the darkness.

U.S. Border Patrol agents and local police gave chase on foot — from bushes to behind homes, then back to the fence.

The conflict escalated. Authorities say they were being pelted with rocks. One agent responded by aiming a gun into Mexico and firing multiple shots at the assailant, killing a 16-year-old boy whose family says was just in the wrong place at the wrong time.