SALT LAKE CITY (AP) — A military veteran who was trying to stop an alleged gunman and inadvertently shot and killed a demonstrator at a Salt Lake City “No Kings” rally was a “safety volunteer” for the demonstration, according to police and organizers.

An estimated 10,000 people were in attendance at the “No Kings” rally that began in Pioneer Park and marched north through the downtown area, the Salt Lake City Police Department said. Gunfire was heard at around 8 p.m., with video posted online showing protesters fleeing in terror.