Updated

An 18-year-old Northern California man is hospitalized in stable condition Tuesday with severe burns after he was set on fire while riding a bus during the previous evening's rush hour commute, authorities said.

The incident occurred when the passenger who was asleep and wearing a kilt-like piece of clothing, was set ablaze by another passenger on the rear of an Alameda-Contra Costa Transit bus in Oakland shortly after 5 p.m. Monday, transit spokesman Clarence Johnson said Tuesday.

The passenger woke up after he noticed his clothing was on fire. He tried to put it out himself when other passengers came to his aid to help put out the flames that severely burned his legs, Johnson said. Once the bus driver realized what happened, he stopped the bus and called for assistance, Johnson added.

The suspect fled the scene before police arrived.

The victim, whose name has not been released, was taken to the burn center at St. Francis Memorial Hospital in San Francisco with second- and third-degree burns, authorities said.

"This is a horrific crime when a human being thinks it's OK to set another on fire," Oakland police spokeswoman Officer Johnna Watson said Tuesday. "Our investigators are working very aggressively to find the person responsible for this senseless act."

No motive has been released as investigators are reviewing surveillance video on the bus, which had at least a dozen other passengers onboard, authorities said.

"We have a lot of witnesses who saw what happened and provided information to the officers on the scene that will help us move this case forward," Watson said.