Salt Lake City police are investigating the roles of two self-described "peacekeepers" following a fatal shooting at Saturday's protest that left one person dead and another injured, raising questions about unauthorized security at public demonstrations.

A bystander was fatally shot after security members at the demonstration confronted a man who was running toward the crowd with an AR-15-style rifle, the police said.

Arthur Folasa “Afa” Ah Loo was described by Salt Lake City, Utah, police officials Sunday as “an innocent bystander.”