WHITTIER, Calif. -- Authorities have identified a man who was found dead on a school bus as a special needs student who regularly rode the bus to his home in Whittier.

The student was identified as Hun Joon Lee by Los Angeles County Coroner's Lt. David Smith, The Los Angeles Times reported.

Lee typically leaves the Sierra Education Center on the bus around 2:30 p.m. and arrives home at 4 p.m., said Brad White, a spokesman for the Whittier Police Department. When Lee didn't show up on Friday, his mother called the school, and the school called the bus company. A driver went out to the bus yard and found the young man in the parked bus, White said.

Police are treating the death as suspicious because "nothing that we've learned so far would lead us to believe he had any medical conditions," White said.

There were no signs of trauma on Lee's body, and no weapons were found at the scene, he said.

The bus driver was held for questioning and later released, White said. No arrests have been made.

Lee attended the center, which has a transition program dedicated to adult students with special needs, said Valerie Martinez, Whittier Union High School District spokeswoman.