US officials have released dashboard camera video showing a white police officer shooting a black teenager 16 times in Chicago last year.
Officer Jason Van Dyke has been charged with first-degree murder for killing 17 year old Laquan McDonald, who police say had refused to drop a knife.
According to the BBC, Mr. Van Dyke said through his lawyer and police union he had feared for his life.
Chicago Mayor Rahm Emanuel has appealed for calm in the city.
Police use of excessive force against African Americans has been the subject of nationwide protests for months.