Two prominent civil rights leaders stood with grieving relatives Wednesday on the bullet-marked block where an unarmed black man was killed in a hail of police gunfire while leaving his bachelor party hours before his wedding.

"We come this morning with the family in their hour of grief," said civil rights activist Rev. Al Sharpton, standing near a makeshift altar of flowers and burning candles near the Kalua Cabaret strip club in the borough of Queens. "We're all family now. Not a black family, not a white family, not a Latino family, a human family."

The community outrage was evident in signs taped on a nearby wall. "Death to Police Brutality and Murder," said one.

A floral wreath showed a photo of the slain bridegroom, 23-year-old Sean Bell, his fiancee and one of their young daughters, with the words: "Love Yourself, Stop the Violence." At least two nearby cars had bullet-shattered windows.

"This is a symbol, not an aberration. Our criminal justice system is broken down on black America, on young black males," said the Rev. Jesse Jackson, who like Sharpton once sought the Democratic presidential nomination.

The victims were black, while the five officers who fired their guns included two blacks, two whites and one Hispanic.

The dead man's fiancee, Nicole Paultre, his parents, and the family of Joseph Guzman, one of the two men wounded in the shooting, were among those attending. William Bell, Sean's father, cried as Sharpton spoke.

Mayor Michael Bloomberg has called the 50-shot police barrage early Saturday "unacceptable," "inexplicable" and a case of "excessive force."

But experts who have studied deadly force say the shooting's confusing circumstances make the mayor's conclusions premature. The amount of firepower, they add, has been given too much emphasis.

"The number of shots fired doesn't mean anything, even though it seems a little shocking," said Jim Cohen, a professor of criminal law at Fordham Law School. "We simply don't have enough information to draw any conclusions."

But at the shooting scene on Wednesday, Sharpton said, "We believe a crime was committed against Sean. We believe a crime was committed against the other two."

"One policeman second-loaded his gun. Ran out and reloaded," he said. "And let me make this clear, that these were semiautomatic weapons. ... They constantly had to pull back each time. ... There was no pause. ... They kept going."

The five shooters — four detectives and one police officer — have mostly remained silent amid an investigation by the Queens district attorney, although lawyers and union officials have said some of them are eager to give their side of the story to a grand jury. All five were placed on paid administrative leave and had their guns removed.

The undercover detective who was the first to open fire has made a statement through his lawyer, according to a report published Wednesday.

Attorney Philip Karasyk told the Daily News that the detective, whose name was withheld, says he identified himself as a police officer and initially held his fire, even after being clipped by Bell's car.

Union officials say the undercover detective who opened fire was convinced there was a gun in the men's car. They also say Bell defied orders to stop and used the vehicle as a weapon.

Still absent are the accounts of two key witnesses: The two men who were partying at the club with Bell. Guzman, 31, shot at least 11 times, and Trent Benefield, 23, hit three times, have remained hospitalized.

Police officials said Tuesday detectives had found a new witness who apparently saw the officers open fire. They were trying to identify more potential witnesses by studying video recorded by a club security camera.

The gunfire on Saturday morning stemmed from an undercover operation inside the club, where a team of officers in plain clothes was investigating alleged prostitution and drug use.

Police said Bell was involved in an argument outside the club, and one of his friends made a reference to a gun.

The detective who was the first to open fire followed Bell and his friends as they headed for their car. As he walked toward the front of the vehicle, they drove forward — bumping him and then crashing into an undercover police minivan, police said.

After the detective fired, the others joined in, police said. One 12-year veteran fired his weapon 31 times, pausing to reload.