Police said Sunday that someone wearing a brightly colored security vest was aiming at a man who had peeled off from the crowd and was holding a rifle.

A 39-year-old man died Saturday night after being shot during Salt Lake City’s “No Kings” protest while a crowd of about 10,000 people marched.

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.