“In 2012, Philadelphia police officers shot 63 people and killed 15, more than any other department in the country except Chicago. Charles Ramsey, who’d been the police commissioner for five years, didn’t like those numbers. He thought the shootings were justified, but he wondered whether his officers could resort to deadly force less often. So he did something local police are typically loath to do, on cases big or small: He called in the feds.”