CHICAGO (AP) -- A federal civil rights investigation looking at one of the nation's largest police departments began in earnest Wednesday, and Mayor Rahm Emanuel will talk with federal investigators Thursday.
Interim Police Superintendent John Escalante told a City Council hearing Tuesday about a planned sit-down between investigators and police brass Wednesday, adding, "We have not been through anything like this before."
Meanwhile Wednesday night, the Chicago Tribune reported that the officer charged in the 2014 shooting death of a black teenager that set off the investigation was indicted by a Cook County grand jury.
The following is a news guide on the Chicago police investigation, where things stand and how it could play out:
U.S. Attorney General Loretta Lynch announced the investigation on Dec. 7 amid protests over the release of a video of the shooting of Laquan McDonald. The 17-year-old was shot by a white officer, Jason Van Dyke, who initially faced a single first-degree murder charge but now has been indicted on six counts of first-degree murder and one count of official misconduct.
Chicago joins 22 other police departments similarly investigated since the start of the Obama administration, including Baltimore and New Orleans.
The Justice Department said Wednesday it is having "productive" talks on police reforms in Ferguson, Missouri, where a probe was opened after the fatal police shooting of 18-year-old Michael Brown in 2014.
Wednesday's meetings in Chicago are most likely get-acquainted sessions. There's no rush: Investigations of far smaller departments have taken a year to finish and the one into Chicago's 12,000-officer force could take longer.
The head of the Chicago police union, Dean Angelo, told WTTW-TV he already met with Principal Deputy Assistant Attorney General Vanita Gupta, who leads the investigation. Angelo described it as an off-the-record talk, saying he conveyed that the union wanted to "help facilitate the moving parts of the investigation."
Emanuel, who's faced some calls for his resignation over the McDonald case, said two members of his administration flew to Washington, D.C., last week for talks on the investigation, but he didn't offer details.
While staff from the Justice Department's civil rights division takes the lead in the investigation, the U.S. Attorney's Office in Chicago will provide support.
Over coming months, investigators will talk to everyone from beat cops to elected officials. Investigators will even ride along with officers on patrol and observe how they interact with area residents.
They'll also go through thousands of police records.
A key component is also community outreach — talking with families of Chicago residents shot by officers, likely setting up a hotline and email for tips, and holding town hall meetings to get direct feedback from the public.
One reason a civil rights investigation takes so long compared with criminal investigations: It is vast. The Justice Department will scrutinize Chicago police from top to bottom as agents try to determine whether there's something systemic in how the department works that leads to violations of citizens' constitutional rights.
Among the many questions federal investigators will answer in a final report: Is there racial bias in the use of force by officers? Are abuses widespread or isolated to a few rogue officers? And do systems that are supposed to hold officers accountable actually work?
The investigation comes first, followed by a publicly released report. Then, Chicago and the Justice Department will endeavor to hammer out a reform road map to bring about wholescale change that sticks.
Most of the time, cities enter agreements voluntarily, the Justice Department said. But sometimes, the sides disagree on critical provisions and must fight it out in court.
According to a copy of the indictment posted on the Tribune's website Wednesday, the charges allege Van Dyke shot McDonald knowing it "created a strong probability of death or great bodily harm."
Van Dyke's attorney, Daniel Herbert, did not immediately return a call from The Associated Press.
McDonald was walking down a street and carrying a knife with a 3-inch blade when he was shot 16 times.
Emanuel is scheduled to meet with Justice Department investigators Thursday. President Barack Obama's former chief of staff said Wednesday that the federal investigation, to which he was initially cool, will bring a "fresh set of eyes" on persistent allegations of police misconduct.
Van Dyke is due back in court Friday.