How do they know that he did or didn't fire if no one stuck around to see it as you outline in this scenario? Because he said so?
Look bro, the police are going to have eyewitness reports of the first person to open fire or publicly point a gun. A ballistics test combined with eyewitness accounts and camera activity from the mall will later prove who was an assailant and who was a reactor. Open and concealed carry is applauded in many states, for the very reason listed in the article. You can stop arguing with me and throwing out ridiculous "what if" scenarios.
Ok Kobe, I did say that people saw you pull out a gun and start firing didn't I? If somebody is already shooting and you see somebody else with a gun are you gonna stop and say 'He's on our side!!'. The average person is gonna be so shocked and panicky and assume the worst which is that they are apart of the problem.
I get what you're saying with all the evidence and all, but that won't be til later. And if people are around then if you shoot you may hit one of them, which fucks everything up for you. Or you do exactly what that guy did which was nothing, and that's the most likely scenario of all.