David Hall crossed West Carson Street about 11:45 p.m. Friday and approached a bus driver who was pulled over in front of the Duquesne Incline.

Mr. Hall wanted to know which bus he should take to get back to his home in Moon.

But as the 24-year-old stepped back from the bus driver's window into the street, a dark-colored sport utility van hit him.

Mr. Hall then was struck two more times by inbound traffic and died at the scene, police said.

All three drivers continued on a short distance before turning around and returning to the scene, said Pittsburgh police Lt. Daniel Herrmann.

But the first driver who struck Mr. Hall lingered for only a couple minutes before taking off again, before police or medics arrived.

"It appears to be an accident," the lieutenant said. "But you can't just leave."

Mr. Hall's mother, Jacquie, said they adopted him when he was 4 years old. She said he had some development disorders that may have made him seem more like a teenager than a 20-something.

Mr. Hall had a fierce independent streak and was not burdened with his disability, his mother said. Friday night he told his mother he was going to Station Square for a concert.

The last time she spoke with him was at 9 p.m. She learned of his death when a police officer arrived at her door at 3 a.m.

"He had a tendency to move real fast and get distracted," Mrs. Hall said.

She pleaded for the driver who left the scene to speak with police.

"We know this was an accident," she said. "But that man will feel a lot better if he steps forward."

Police suspect the first driver may have been drinking or had something else in his system that he didn't want police to know about.

No charges are expected to be filed against either of the other drivers.

"They accidentally ran him over," Lt. Herrmann said. "One person didn't know what it was."

Police described the first driver as a stocky white man in his 30s, 5 foot 6 or 5 foot 7 tall with black hair that was slicked down.

He was driving a dark, mid-size SUV, which possibly has front-end damage from striking Mr. Hall.

Anyone with information on the driver is asked to call the Pittsburgh police homicide unit at 412-323-7161.