MOKOLO, Cameroon — As the convoy barreled through a village in northern Cameroon on Monday, a 7-year-old boy darted to the road, excited to see the chain of white S.U.V.s carrying Samantha Power, the first cabinet-level American official to visit the country since 1991.

Distracted by a thundering noise, the boy glanced up at the helicopter providing security from above. Suddenly, he was struck dead — killed by the same convoy that had brought officials to showcase American efforts to help protect West Africa’s women and children.

After hitting the boy, one S.U.V. carrying State Department employees pulled to the side of the road. The rest of the motorcade continued on its way.

“Oh, my God,” Ms. Power said later, after she was informed of the tragedy, according to her spokesman, Kurtis Cooper. “I want to go see his family,” she added, and later she did.