Chief Jon Belmar said at a news conference that officers had been tracking the man, who they believed was armed, during a protest marking the death of Brown, the black, unarmed 18-year-old whose killing by a white Ferguson police officer touched off a national "Black Lives Matter" movement.
The man approached the officers, who were in an unmarked police van, and opened fire, Belmar said. The officers returned fire from inside the vehicle and then pursued the man on foot when he ran.
