The unarmed man fatally shot by an off-duty Baltimore police officer outside a Mount Vernon bar early Saturday had his hands in the air when the officer fired 13 rounds, striking him nine times in the chest and groin, according to department sources.

Two top police commanders said Thursday that four witnesses — two friends of victim Tyrone Brown and two bystanders — corroborated that version of events in taped interviews with homicide detectives and prosecutors.

The commanders acknowledge that three other witnesses who were with Gahiji A. Tshamba said that he identified himself as a police officer and that Brown shoved Tshamba, events that would be more favorable to the officer's case. But police say the version of events described by those witnesses is inconsistent with evidence recovered at the scene and other findings of the investigation.

Police sources with knowledge of preliminary autopsy findings said the medical examiner found a heat imprint from a muzzle blast on Brown's shirt, a condition known as stippling. Such an imprint is created when a weapon is fired from as close as five inches away. The finding could be used to show that Brown was executed at close range, but it could also indicate that he was shot while advancing on the officer.

Police officials, who requested not to be identified in part to distance themselves for now from a highly sensitive case, have taken the unusual step of releasing details of an investigation as part of an effort to defuse public anger that Tshamba has not been charged with a crime.

They say they are frustrated that prosecutors might extend the investigation into next week, delaying the arrest of the 15-year veteran officer.

Officials with the Baltimore state's attorney's office declined to comment on the investigation. State's Attorney Patricia C. Jessamy said during a radio appearance Thursday that her department was "moving forward expeditiously."

Police worry that further delays will add to mounting public suspicion that authorities are protecting one of their own. The unusually harsh criticism, shrouded behind anonymous sources, appears designed to shift public anger over Tshamba's not having been arrested to the prosecutorial arena.

"We handed prosecutors our case Monday morning," said one top police official, who spoke on the condition he not be named. The lead investigator on the case "has slowly interviewed everyone and went to the crime scene. That's fine, but our position is we would like to proceed as soon as possible."

Said another commander: "In this case, the best we can see, there is no reason for this man to have been shot as many times as he was. Homicide is convinced that the evidence is very clear. This is not a complex case. … There was no physical confrontation. He had his hands up when he was shot."

Speaking with Clarence M. Mitchell IV on WBAL radio, Jessamy said she planned to meet with prosecutors Friday to discuss the case. But she cautioned that doesn't mean charges are imminent.

"I'm not the general public," Jessamy said. "I can't offer opinions. I have to make decisions based on the law, the facts and the evidence. … We will be moving forward expeditiously."

Despite a swift police investigation, prosecutors say they are awaiting the autopsy report and want to talk with officers who responded to the scene. They have already reinterviewed the seven witnesses.

Privately, officials in the prosecutor's office note that because this is Tshamba's second off-duty shooting of a civilian in five years, they want to make sure the case is handled properly.

In 2005, Tshamba was driving under the influence of alcohol when he got into a confrontation with a group of young men in a sport utility vehicle who he said shouted racial epithets at him. Tshamba followed the car into a residential neighborhood, where the other driver turned his vehicle and rammed the officer. Tshamba chased the men into a wooded area, firing his weapon. A juvenile was hit in the foot.

Tshamba received an eight-day suspension for the incident but avoided criminal charges and dismissal. Prosecutors now privately question whether top police administrators were too lenient in allowing him to remain on the force. As one official said: "They expect us to clean up their mess."

Officials in both the department and state's attorney's office say the pressure from the public, the news media and within their own offices has made the investigation complex and politically charged. One official in the prosecutor's office cautioned that many cases "are not as easy and cut-and-dried and slam-dunks as people want us to believe."

Andrew C. White, a former federal prosecutor who is now a defense attorney, said the state's attorney's office should proceed slowly to build a solid case.

"I think the prosecutors are trying to strike a balance between speed and accuracy," White said. "In the immediate aftermath of a shooting, oftentimes it is not clear if a person acted in self-defense. ... Public opinion has no bearing. You put yourself in a box if you arrest too soon."

White said that when a shooting involves a police officer "who is trained to recognize situations that are rapidly unfolding, you have to give some credit to what the officer says in defense of why he discharged his firearm. …He gets the benefit of the doubt. Whether it's appropriate or not is a question, but he gets it."

Tshamba remains on desk duty without his gun and badge. Meanwhile, Brown's family has hired an attorney, Andrew D. Freeman, and have announced the funeral for 10 a.m. Wednesday at the Morgan State University auditorium.

The shooting involving Tshamba occurred early Saturday after he and Brown found themselves in an alley off Eager Street and near the back door to Club Hippo.

Brown, a former Marine, touched the officer's female companion, who took exception to what Brown apparently thought was a joke. Brown sister, who witnessed the exchange, said her brother apologized and tried to walk away but Tshamba challenged him.

Police said the officer took out his department-issued Glock and fired 13 rounds from feet away, hitting Brown nine times. Detectives are trying to determine whether Tshamba was impaired by alcohol. The officer has declined to talk to homicide detectives, and he refused to take a breath test.

Once detectives heard from some witnesses that Tshamba might have identified himself as a police officer, investigators treated the probe as a police-involved shooting, meaning any charges would be left for prosecutors, who take all such cases before a grand jury, which adds time before an arrest is made.

One police commander said arresting Tshamba on the spot would have been irresponsible. They didn't know whether he had consumed alcohol, needed to review recordings from a surveillance camera near the shooting scene (later found to be inoperable) and listen to 911 calls, he said.

Tshamba, like any citizen being investigated in a possible crime, does not have to speak to detectives. Unlike a civilian in the same predicament, he cannot be detained and is free to leave to consult an attorney, a right afforded him under his labor contract.

And not every civilian involved in a homicide is arrested immediately. The Johns Hopkins University student who killed an intruder with a samurai sword in the fall of 2009 was questioned by detectives but never arrested or charged. Prosecutors later ruled the killing self-defense. Similarly last year, a dry cleaner and a gas station attendant were never arrested after they shot robbers, and both were later cleared.

Jessamy's office has feuded with city police for years on a variety of issues, including arrest policies, the creation of a list of officers deemed too untrustworthy to testify in court and the thoroughness of police investigations.

Prosecutors have lost or dropped several criminal cases against police officers because of botched probes or missing evidence, including two rape cases in 2007 and a misconduct case in 2001 involving an officer accused of planting drugs on an innocent man.

"There is a reason we are going carefully," one official in the state's attorney's office said of the case being built against Tshamba, "and it's because if we get to trial a year from now, we want to make sure this is right."