Two days after police shot and killed an unarmed man in Queens, critics are questioning police procedures for undercover investigations and city officials indicated that the shooting could lead to policy changes in the police department.

The police commissioner, Raymond Kelly, said that the procedure followed by the undercover detective who first opened fire at the club in Queens was “unusual.”

The undercover detective who was investigating possible illegal activity at the Kalua Cabaret did not carry a gun or badge when he entered the club because a bouncer was patting down bar-goers, but retrieved them later and later confronted a group of men who he suspected were going to use a gun in a dispute.

By confronting the men himself, the detective apparently violated police protocol which usually calls for an undercover officer to let back-up officers in uniform arrive. Instead, the detective made first contact, which Mr. Kelly said was “unusual.” Police experts said the policy of having uniformed police make arrests insures that suspects know that they are dealing with police.

Mr. Kelly said that when an undercover detective suspects a gun may be involved, the detective can take the initiative.

The undercover detective jumped on the roof of the car wearing a badge around his neck, but it is not clear if the detective identified himself as a police officer or if the men in the car recognized him as one. The car, which struck the officer, then reversed into a shuttered garage before crashing again into the minvan, prompting four detectives and one police officer to fire a fusillade of 50 bullets at the car, hitting it 21 times.

All five officers who fired their weapons, including an officer with 12 years on the job who fired 31 shots, have been stripped of their weapons and placed on administrative leave while the Queens District Attorney investigates the case.

Sean Bell, 23, who was celebrating his bachelor party and planning to get married on Saturday, was killed. He had four bullet wounds. Joseph Guzman, 21, was hit by 11 bullets and was listed in critical, but stable condition. Trent Benefield, 23, was in stable condition with three bullet wounds. No weapon was found in the car or at the scene, police said.

Mr. Kelly disclosed that one of the two undercover detectives who didn’t fire his weapon had drunk two beers at the bar over a period of several hours to blend in with the crowd. The commissioner said that he didn’t know if the detective who opened fire had been drinking, because the police aren’t allowed to interview the officers until the district attorney finishes the investigation. It is standard police policy to allow undercover officers to consume two drinks, Mr. Kelly said.

The number of shots fired was also contrary to police training, Mr. Kelly said, in which officers are taught to fire three shots and then stop and assess the threat.

The average number of shots fired in a police incident for the year through November 19th was 3.8, down from 5.04 for the same period in 2005, police said.

The mayor said the shooting “seemed excessive” and questioned why police fired “50 odd shots.”

The president of the Detectives Endowment Association, Michael Palladino, criticized the mayor, saying: “So much for withholding judgment before all the facts are in. I think his comments unfairly taint the entire situation.”

The union’s lawyers are representing the four detectives involved in the case, Mr. Palladino said. “I think it is important to point out that we have contacted the Queen’s District Attorney’s office, and our detectives are anxious and ready and willing to be interviewed by the district attorney’s office and testify before the grand jury in an effort to get the facts of the story out,” he said.

A former police officer, Eugene O’Donnell, who is a professor of police science at John Jay College of Criminal Justice, said the incident would likely result in a “top-down” review of procedures involved in vice operations. The detectives involved in the incident were part of a citywide task force to reduce crime at nightclubs and shut down establishments that turn a blind eye toward wrongdoing. The Kalua Cabaret had a record of allowing prostitution and drug consumption, police said.