CHICAGO (AP) — A white Chicago police officer who shot a black teenager 16 times last year was charged with first-degree murder Tuesday, hours before the city released a video of the killing that many people fear could spark unrest.City officials and community leaders have been bracing for the release of the dash-cam video, fearing the kind of turmoil that occurred in cities such as Baltimore and Ferguson, Missouri, after young black men were slain by police or died in police custody.A judge ordered that the recording be made public by Wednesday. Moments before it was released, the mayor and the police chief appealed for calm.“People have a right to be angry. People have a right to protest.