“We had every injury type that you can imagine for a scenario like this,” Jeffrey S. Paul, the director of the Morris County Office of Emergency Management, said outside Morristown Medical Center. “It’s tragic for anybody to be in a situation like this. But children — our hearts certainly go out to the families.”

The force of the collision ripped the front cabin from its chassis, and the mangled yellow bus lay twisted in the grassy median between the eastbound and westbound lanes on Interstate 80. Debris from inside the bus — a pair of Nike shoes, reusable water bottles, a black jacket and snack bags — was strewn about the grass.

The children were wearing seatbelts, the police and passengers said.

One student, Theo Ancevski, 11, described the pandemonium that followed the crash, with his classmates screaming and “hanging from their seatbelts” as others scrambled out windows and a rooftop emergency exit.

“I heard a scraping sound and we toppled over the highway,” said Theo, who sustained only minor cuts. “A few people got out of the windows and they got out of the emergency exit at the top of the roof.”

Officials did not release the name of the child who was killed in the crash. Jennifer M. Williamson, the teacher who died, grew up in Paramus, her cousin said, on a tree-lined block not far from the school where she taught fifth-grade social studies. She declined to give her name.