Would I have been able to stop the murder? Who knows, I wasn't there. We can debate this until we're blue in the face. The outcome would still be the same. Don't know about you, but if I saw someone come out of the restroom brandishing a handgun, I'd take cover and draw my firearm and look for an avenues of escape. If there's no clear path to an exit, I would prepare to shoot my way through the guy if necessary. As far as I'm concerned, he became a "threat" the minute he came out of the restroom brandishing.
From what I read, it seems like the whole incident took several minutes. In any case, I would rather see the incident ending by some law abiding CCW license holder double tapping the perp rather than him taking his own life. Wouldn't want it ending on "his terms". He decided his fate the minute he chose to become a threat to innocent people.
As for this being a good reason why we shouldn't have firearms, I disagree. As soon as the guy appeared with the firearm, a properly trained and licensed firearms holder would have recognized the threat and been able to neutralize the threat before causing the maximum amount of damage.
We can't read minds, so it's impossible to see how many people the BG wants to hurt, kill, etc. All I know is that when a BG poses a threat, I want it to end on my terms, not his.
gf