SIX CORNERS BACKSTAGE GUIDE 11 Mr. Emanuel acknowledged there had already been decades of complaints and past pledges for change, but he called the report “a moment of truth for the city.” “It’s right to say, with a slightly skeptical eye, ‘What makes us believe you’re going to be sincere in following through,’ ” Mr. Emanuel said, adding that changes to police procedures over the last year should reassure residents of his intentions. He promised to act locally and work with federal officials in the months ahead. “There’s a difference between holding people accountable and being cynical,” said Mr. Emanuel, who in his second term as mayor has been battered by criticism over Chicago’s rising violence and mistrusted Police Department. By proceeding with an overhaul of policing, Mr. Emanuel may buy himself some maneuvering room to argue he is bringing the problem under control. The report described a broad lack of oversight within the department. In some cases, officers reported that they had used force such as punching in order to restrain combative suspects, but video evidence reviewed by investigators frequently showed that officers’ use of force was unnecessary. “We found that officers engage in tactically unsound and unnecessary foot pursuits, and that these foot pursuits too often end with officers unreasonably shooting someone— including unarmed individuals,” the report said. “We found that officers shoot at vehicles without justification and in contradiction to C.P.D. policy. We found further that officers exhibit poor discipline when discharging their weapons and engage in tactics that endanger themselves and public safety, including failing to await backup when they safely could and should; using unsound tactics in approaching vehicles; and using their own vehicles in a manner that is dangerous.” Chicago’s police superintendent, Eddie Johnson, said that some findings were “difficult to read” and that he wanted to expand training and mentoring for officers. “While I’m optimistic and hopeful about the direction that we’re heading in,” Mr. Johnson said, “I’m realistic about the fact that there is much, much, much more work that needs to be done.” Leaders of the union that represents rank-and-file officers questioned the timing of the report and the speed with which the investigation was conducted. “What also remains to be seen is whether or not the report might be considered compromised, or incomplete as a result of rushing to get it out before the presidential inauguration,” the union said in a statement. Several activists said the findings were unsurprising, but welcome. They urged sweeping reforms to the Police Department, but expressed little confidence that they would take place. “The decision that D.O.J. made today, I said it a long time ago: that the system is corrupt,” said Dorothy Holmes, whose son was killed by a Chicago officer in 2014. “We want accountability. We want these officers charged as criminals, as they would charge one of us with something.” Chicago officials have been bracing for the findings after more than a year of tense public debate about the Police Department and its long, troubled history of community relations, particularly with African-American and Latino residents. Announced in December 2015, the investigation began in a year of cascading violence for the city. In 2016, there were 762 criminal homicides in Chicago, more than in New York City and Los Angeles combined. The inquiry was spurred by the city’s reluctant release of a chilling video that showed a white police officer shooting a young black man, Laquan McDonald, 16 times. For months, the city fought to keep the dashboard camera footage from being made public, but a judge ultimately ordered its release. Residents were outraged by the images, and some marched in protest and demanded that Mr. Emanuel resign. Long before the latest findings, the critiques of the Chicago police were stark. Two years ago, the city announced reparations and an apology to black men who had said they were tortured and abused in the 1970s and ’80s at the hands of a “Midnight Crew” of officers overseen by a notorious police commander. Last year, a task force appointed by Mr. Emanuel issued a scathing report that concluded that racism had contributed to a long pattern of institutional failures by the police. City officials said that they were already making substantive changes—separate from whatever the Justice Department would announce. Mr. Emanuel’s aides pointed to changes the mayor has called for in improved officer training and equipment. All Chicago patrol officers are to have body cameras by the end of 2017. But police shootings have persisted, and some say changes have not come fast enough. Just weeks after the Justice Department began its investigation, an officer shot and killed two people: a teenager said to be wielding a bat, and an elderly neighbor hit by a stray bullet. That officer later sued the estate of the teenager he killed, claiming emotional trauma. Last summer, another officer fatally shot an unarmed teenager in the back as he was running away. Lori E. Lightfoot, president of the Chicago Police Board, said, “I don’t think that the pressure will be off” when Mr. Trump takes office because of local activism on police issues. Ms. Lightfoot, who was chairwoman of the mayoral task force that released the report last year, said she was encouraged by Mr. Emanuel’s remarks on Friday but wanted concrete actions from him in the weeks ahead. “We are going to demand that the reforms happen,” she said.