A special prosecutor will be appointed to investigate Chicago police officers who were on the scene when 17-year-old Laquan McDonald was killed, Cook County Judge Vincent Gaughan said Friday.

Officers claimed in written reports that McDonald had moved menacingly toward them just before one of the cops, Jason Van Dyke, fatally shot him. A video of the shooting contradicts those claims.

Gaughan had already decided to appoint a special prosecutor in a murder case against Van Dyke in connection with the shooting. On Thursday, the judge said he would name that special prosecutor in August.

Friday’s order says a special prosecutor “shall be appointed in the [shooting] matter for the purpose of investigating and, if necessary, prosecuting any wrongdoing on the part of Chicago Police Department personnel.”

The order, which does not specify how many special-prosecutor offices there will be, came in response to a February petition by civil-rights groups for the case to expand to other officers on the scene. The petition accuses them of covering up “egregious police misconduct.”

Gaughan referred the alleged cover-up to the court’s presiding criminal judge, LeRoy Martin Jr., who could impanel a grand-jury for the investigation and appoint the special prosecutor.

The move elated attorneys for the civil-rights groups. “Nothing until today has started to happen with respect to the other officers who were on the scene and involved with the coverup,” said Locke Bowman, one of the attorneys.

“We could not be more pleased with this order from Judge Gaughan,” Bowman said. “If the Chicago Police Department had had its way, if no videotape had surfaced of how that shooting had happened, the false account in the police department’s official records would have become the quote-unquote truth about how Laquan McDonald met his death.”

Minutes after Gaughan’s order, Martin held an unscheduled hearing with the civil-rights attorneys, who hand-delivered him a letter that recommends a team of special prosecutors, including former federal judge David Coar and former federal prosecutors Sergio Acosta, Ronald Safer and Patricia Brown Holmes.

“All have informed us that they would agree to accept appointment to a special-prosecutorial team,” the letter says. “The team must reflect the diversity of Chicago’s community. Laquan McDonald’s death brought international attention to the reality of police brutality in Chicago, a reality that has long been known to Chicago’s African American community.”

Martin set a July 15 hearing about the case involving the other officers.

Cook County State’s Attorney Anita Alvarez withdrew her office from the Van Dyke case in May after insisting for months that her ties to police officers posed no conflict of interest.

The letter from the civil-rights groups proposes a single special-prosecutor team to handle both Van Dyke’s murder case and the probe into the other officers’ conduct. Another possibility is the creation of parallel special-prosecutor offices.

Federal officials are also looking into possible charges against the officers.

McDonald died October 20, 2014. Van Dyke allegedly fired 16 shots into him. More than a year later, a court ordered the city to release the video, recorded by a police dashboard-camera. The video sparked a public outcry, calls for a police-accountability overhaul, and a U.S. Justice Department investigation of the city’s policing.

Van Dyke’s attorney, Daniel Herbert, declined to comment on his way out of the Leighton Criminal Court Building on Thursday. He said a “gag order” had been issued in the case.

Chip Mitchell reports from WBEZ’s West Side studio. Follow him on Twitter @ChipMitchell1 and @WBEZoutloud, and connect with him through Facebook, Google+ and LinkedIn.