Three days had passed before I saw a police officer in Detroit. I’d covered miles of the city, by foot and by car. Twice I was advised not to bother calling the police in an emergency; they wouldn’t come. I only ever found them in one place: armed officers from the city’s police department and from Detroit Public Schools’ own security force were manning a gray metal detector at the door to Martin Luther King Jr. Senior High School, on East Lafayette Street. They were in position for a public meeting that night, in May, asking that everyone empty…