I wonder how many drew their guns before assessing the situation. One of the things emphasized in my target id class last months is not automatically drawing when you hear a gun shot. you can clear your garment and have your hand ready to draw but that may not be the best solution. Remember the guy in Nevada who engaged the one criminal before assessing the situation and the criminal’s backup killed him. All that being said ccw folks will be first responders either engaging the active killer or providing trauma first aid before EMTs are allowed on scene.
I’m a firearms instructor myself.
I understand your reasoning, and it’s sound. That being said, us “sheepdogs” have a natural reaction to go into “Defend and Protect” mode.
My guess is that’s what happened. Folks had their kids there, wives, mothers, etc., and they were putting their bodies and their firearms in the path between scumbag perp and their loved ones.