DAHYAN, Yemen — The boys crammed into the bus, their thin bodies packed three to a seat, with latecomers jammed in the aisle. They fidgeted with excitement about the day’s field trip, talking so loudly that a tall boy struggling to get their attention put his hands over his ears and yelled.

Hours later, most of them were dead.

During a stop for snacks in the poor village of Dahyan in northern Yemen, an airstrike by the Saudi-led coalition of Arab nations hit nearby, blasting the bus into a jagged mass of twisted metal and scattering its human cargo — wounded, bleeding and dead — in the street below, according to witnesses and parents.

“My leg is bent,” cried a young boy covered in blood, examining his damaged limb. “A jet hit us,” he said in a video taken at the scene after the airstrike.

Yemeni health officials said 54 people were killed, 44 of them children, and many more were wounded.