Republican presidential candidate Ben Carson is calling a video showing a white Chicago police officer fatally shooting a black teen "very disturbing." And he says the city's delay releasing the footage was "a failure of government." Carson spoke Thursday in Chicago, where video of the 2014 shooting of Laquan McDonald released last month has prompted protests and a Justice Department investigation of the police department. Carson is the only black candidate in the 2016 presidential field. He wouldn't say whether he believes Mayor Rahm Emanuel should resign. He says people in Chicago should decide.