Witnesses are saying that he came in the right side emergency door near the screen, walked in the door, walked up the aisle, then walked back out, then he waited a little while, then he walked back in and just SAT there a MINUTE just creepy staring into the crowd, before he threw the CS gas canisters, then once they started to put out smoke, that's when he just started to open fire and gun people down.
A legal carrier would have had to time get his firearm ready and he could of at least started shooting back, instead of everyone just laying there in the fetal position or running away to be shot in the back. He may have even got lucky if he was well trained and either turned his attention to the shooter so others could get away, or even PUT the guy down with a head or pelvic shot if the rounds wouldn't have penetrated his vest.
I still hear that you can crush ribs if you hit a Kevlar vest just right, and you can also penetrate most with .357 Sig or .357 Mag or 44 Mag. You don't need a rifle round to penetrate some Kevlar. I doubt the guy was rocking plates bro.