A young man allegedly involved in a fight aboard a BART train was shot to death by a BART police officer on the platform of the Fruitvale Station early New Year's Day, in the midst of a brawl between two groups of young train passengers.

Oscar Grant, 22, was shot once while on the platform after a BART officer drew his gun during what officials called a volatile and chaotic scene. A gravely wounded Grant was taken to Highland Hospital, where he died Thursday morning, the Alameda County coroner's office said.

While witness accounts reported by news organizations indicate Grant was on the platform and handcuffed when he was shot, BART spokesman Jim Allison said the victim was not restrained when the gun discharged. BART officials wouldn't comment on whether the shooting was accidental or deliberate.

"Any incident with that many people, you're going to have different perceptions of what happened," Allison said.

Officials said no weapon was recovered from Grant or others involved in the altercation.

Witnesses' account

Allison and witnesses gave this account of the events leading up to Grant's death:

Apparently, two groups of young men were fighting on the train, which had come from San Francisco. Sometime while the train was en route to Dublin/Pleasanton, BART's operations control center learned of the disturbance and dispatched five BART police officers to the Fruitvale Station about 2 a.m. The train was ordered to stop and hold at Fruitvale so the police could deal with the situation.

The train arrived at Fruitvale, and police began trying to isolate the young men as they fought. Officers believe the group included Grant.

As officers attempted to control the situation, the two groups apparently continued to scuffle on the platform. At one point, three or four individuals on the platform were handcuffed, Allison said. Two people involved in the scuffle were detained, questioned by police and later released.

On Thursday afternoon, BART officials held a news conference and confirmed the officer had drawn his weapon during the incident. In describing the incident, however, they chose their wording very carefully, repeatedly referring to the shooting as a weapon "discharge," without specifically saying that the officer shot Grant.

Grant lived in Hayward, where family and friends gathered Thursday evening, too distraught to talk about the incident.

They would only say that he leaves behind a 4-year-old daughter.

At a park around the corner from his home, dozens of his friends gathered to share stories and express sadness over his sudden death.

"I knew Oscar for 19 years," said friend Robert Johnson. "He was everything. He was the world."

When a Chronicle reporter tried to interview other friends of Grant, a grief-stricken relative asked the group not to talk to reporters.

At the news conference, BART Patrol Cmdr. Travis Gibson said officers are trained to pull their guns when a BART patron or an officer is in danger.

"You use what force is reasonable to neutralize the situation without the person losing their life or the officer their life," he said.

Gibson said New Year's Eve had been a chaotic night for the officers on duty, with one gun recovered in San Francisco and another in West Oakland.

Officer tested, put on leave

The officer involved in the shooting was not identified, but Allison said he had been on the force nearly two years. The officer was given an alcohol and drug test, per department policy, and placed on administrative leave. Results of the alcohol and drug test are pending.

"It's too early to go into the specifics of the officer's record," Allison said.

Officials said the officer was carrying a baton in addition to his gun, but they were unsure whether he also carried a stun gun.

BART police have launched an internal investigation as well as a criminal investigation into the incident. The Alameda County district attorney's office has opened its own investigation, Allison said.

The Fruitvale Station has cameras, but BART officials said they are used only for monitoring and are not capable of recording. Some BART stations do have cameras that can record events, but not all of them.

Oakland attorney John Burris, who has handled several high-profile cases involving police shootings, said the incident prompts several questions to determine whether the shooting was justified.

Burris said he would want to know why the officer believed deadly force was required and whether the victim had a weapon or posed an immediate threat, or, if the shooting was accidental, why the officer's gun was drawn.

"The question is whether the person's civil rights have been violated," he said.

BART police ask anyone with information about the incident to call (877) 679-7000, extension 7040.

The BART police force has 206 sworn officers, many of whom were patrolling the system on New Year's Eve. The trains were running on extended service until 3 a.m. to accommodate late-night partygoers.