Seven police officers were hit on Tuesday with disciplinary charges in the 50-shot slaying of an unarmed groom-to-be on his wedding day — a case that has sparked protests and raised questions about police firepower.

If found guilty at an internal trial, the officers — including three shooters acquitted last month at a criminal trial and their supervisor — could be fired. A union official said Tuesday that they would fight the allegations.

Police officials described the move as procedural, citing administrative guidelines requiring them to bring charges against officers within 18 months of the incident.

The New York Police Department could take "further administrative steps" once the U.S. Attorney's office in Brooklyn completes a review of the case, said NYPD spokesman Paul Browne. Federal prosecutors have declined to discuss possible civil rights charges.

Sean Bell, 23, died in a hail of 50 bullets on Nov. 25, 2006 around the corner from a Queens topless bar where he had a bachelor party and where undercover police were investigating complaints of prostitution. Two of his friends were seriously wounded.

At a two-month trial in Queens, detectives Gescard Isnora, Michael Oliver and Marc Cooper said they opened fire on Bell's car because they believed he and his friends were armed, and because they defied orders to halt and tried to drive away. No weapon was recovered.

Last month, the three were cleared of manslaughter and other charges. A judge, who heard the case instead of a jury, said in a decision that prosecution witnesses who testified that the officers opened fire without warning lacked credibility.

The department last year served charges against Isnora, Oliver and Cooper with administrative charges "which basically mirrored the criminal charges they faced as a result of their indictments," Browne said.

On Tuesday, additional charges were filed accusing the three detectives and one other shooter who wasn't charged in the criminal case with firing outside of police guidelines. Isnora, who followed the men and fired first, also was charged with "taking enforcement action while acting in an undercover capacity while other non-undercover officers were available," Browne said.

In addition, the department accused a lieutenant of failing to properly plan the undercover operation, and two more detectives of failing to properly process the crime scene.

A fifth officer who fired his gun wasn't charged.

Detectives' Endowment Association Michael Palladino said the union would "defend these detectives in the (NYPD's) trial room as vigorously as it did in court."

The Rev. Al Sharpton called on the NYPD to immediately fire the officers, saying there "must be no tolerance for crime but also no tolerance for police misconduct."

Earlier this month, Sharpton led a protest against the not-guilty verdict in which more than 200 people were arrested for blocking entrances to bridges and tunnels.

The new administrative charges were first reported Tuesday on the New York Post's Web site.