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.

The alleged rifleman, Arturo Gamboa, 24, was also shot and was taken into custody on a murder charge, Salt Lake City Police Chief Brian Redd said at a Sunday news conference. The bystander who was killed was identified as Arthur Folasa Ah Loo, 39, a fashion designer from Samoa.