LA CRESCENTA  (AP) — A 15-year-old boy plunged to his death from a suburban Los Angeles school building in front of classmates on their lunch break Friday in what may have been a suicide, authorities said.

The 10th-grader plummeted from a three-story building at Crescenta Valley High School shortly before 12:30 p.m., said Sgt. Booker Hollis of the Los Angeles County Sheriff's Department.

A preliminary investigation indicated that the boy jumped, but an accidental fall was not immediately ruled out, Hollis said.

The boy, whose name was not released, was alone when he fell in a central location on the campus where two buildings are connected by elevated walkways. It was unclear whether he fell from a walkway or the roof, said Richard Sheehan, superintendent of the Glendale Unified School District.

There was no indication that the boy had been bullied, Sheehan said.

"I'm sure when this is all said and done, we will still not have all the answers," he said.

The fall happened at the beginning of the lunch period at the school, which has 2,950 students, Sheehan said.

Michael Kim, a ninth-grader, said he "heard a thump" as he was leaving his classroom on the third floor to go to lunch.

Jubilant for the weekend ahead, Kim says he and friends were singing a Top 40 hit as they headed to the quad.

When the 14-year-old and his friends got there, they saw a big crowd and the boy's body.

"I was pretty much just shocked. My jaw just — it dropped," Kim said. "We never expect something like that in this kind of neighborhood at this school," he said.

A crisis center was immediately set up in the cafeteria, and students who may have witnessed the fall were encouraged to give information.

The school halted classes, and students were directed away from the school quad where the boy died to an athletic field, where parents came to pick them up.

Classes will resume Tuesday. Monday is a school holiday.

La Crescenta is an unincorporated foothill community about a dozen miles northeast of downtown Los Angeles.

Kim said the mood on campus changed quickly as news spread about the death. The school doesn't have a bullying problem, he said, but sometimes teens can joke callously.

"It's just weird because everyone just started caring" about each other, said Kim. "One person changed an entire school in 20 minutes."