A prosecutor on Wednesday cleared a Charlotte police officer in the killing of a black man whose death touched off civil unrest, and he presented detailed evidence to rebut assertions that the slain man was unarmed.

Officer Brentley Vinson was justified in opening fire on Keith Scott and won't face charges, Charlotte-Mecklenburg District Attorney Andrew Murray said.

In a 40-minute news presentation to news reporters, Mr Murray produced evidence that Mr Scott was armed with a handgun and the officer who killed him feared Mr Scott would shoot.

The announcement "profoundly disappointed" Mr Scott's family, but they haven't decided whether to file a lawsuit, their lawyer said.