[Ruy Dias de Bivar]

*** Had but one - ONE - citizen in the the theater been lawfully armed, this tragedy could have been avoided.***

I doubt that. He had on body armor head to toe. An armed citizen shooting back might have shook him up so he might have missed a few. Now, if the citizen had a .30 Tokarev or a FN 5.7 mm he might have gotten through some of the armor.

[agere_contra]

I hear you, but body armor isn’t a personal defense shield: there are gaps and weak spots. This is why they don’t test it by standing in a hail of bullets.

Inside leg, armpit, eyes, inside hand, gun, waistband - just fire enough and you might get a lucky hit.

Plus he’s not a grizzly bear: impact from a few hits might have knocked him down or spun him round.

[ThermoNuclearWarrior]

Someone having a gun isn't going to guarantee a better ending to something like this, but it does significantly improve the chances of it. You don't hear about these types of shooters having shootouts very often because they commit suicide or surrender as soon as they are met with force, or usually before they are met with force, but know it's close. I think this guys mind would have turned towards retreating and surrender as soon as someone shot at him. There are several other cases where evidence shows the shooters in those cases would have likely committed suicide as soon as confronted by an armed civilian the same as they did when confronted by law enforcement.

[CodeToad]

Shoot him in the head, neck, legs, crotch, arms, anywhere would have stopped him.