LOS ANGELES — Harley Hoyt, an 18-year-old senior at Valhalla High School in San Diego County, was listening to his headphones to pass the time during the 12-hour bus ride up California’s Interstate 5 when he was catapulted forward, his face smashing against the seat in front of him.

All around him, people were screaming. The front of the bus was “like an accordion,” he said. A truck outside was on fire. He kicked the emergency door open and jumped out.

“Everyone was piling out the windows,” he said. “It was like a battle scene. People were screaming, crying, pulling out their hair. Everyone was bloodied. My clothes were covered in blood.”