Dubious to that. Basically you're saying you're in a pressure situation, where I'm assuming you're likely to have fuck all fine motor skills, that you're going to be able to draw your weapon, load a bullet into the camber, remove the safety etc, acquire the target and let off a round accurate to drop the dude. Yeah, I'm calling bullshit.

Do some research into these shootings and I'll tell you what is likely to happen:

You're walking along thinking about what kind of coffee you going to get. Suddenly you may hear gun fire, if you're lucky enough to have not had your head blown off on the first folly, you would likely either freeze or drop to the ground while your mind tries to take in what the hell is happening, by the time you've stopped hesitating and worked that it's some gutless cunt who's started firing into the crowd they've probably already emptied whatever they have in their magazine and ran away.

I suppose it's possible that if they're mental enough they might try to reload to have another go. And I suppose that in that space of time you might have the opportunity to draw your weapon - if you remember that you have it - load and shoot the guy - despite that fact that your whole body would be shaking like jello, no matter how stone cold you think you are. And you might be able to fire off maybe a few rounds. But the more likely thing to happen is that you'll either just blow your own balls off, shoot some innocent bystander, or the guy will simply notice you're packing heat and shoot you while you're still fumbling with your weapon. All just down to the mental space you're in.

Hell, even if by some miracle you're able to hit them then it's still possible that they're able to do huge amounts of damage. Contrary to Hollywood it's possible that people still able to operate even if they've have been hit by gunfire for at least some time. Also, if they're at least organised I.E., terrorists, then you'd assume that they would be at least intelligent enough to stagger their firing so you would have one guy firing while the other guy was loading. The trend with these guys seems to be in working in teams two now rather than your individual psycho that you used to have to worry about. So it's possible that you wouldn't even get that opportunity.

I'm not saying that it's not possible to drop the guy just that it's unlikely. And it seems to me that if you look at things objectively - disregarding the politics - that purely in the context of these situations where the gunman or potential gunmen very much have all of the initiative that it's unlikely that even if you have a weapon that you're going to be that much good at all in returning fire.

I suppose if you're charitable that it's possible that maybe the situation will degenerate into a hostage situation or the gunman may start opening up closets or looking under tables to kill potential victims that have sort refuge, where camping with a gun pointed at the entrance may kill the dude, but to me it doesn't look like it would matter much if you were packing or not. Due to the unlikeliness of this situation IMHO.

Sorry but concealed carrying while there may be other good arguments for it is not going to be solution to mass shootings if you research how these events usually go down. I.E., quick and brutal attacks conducted by cowards.