There's a lot wrong with this comment but I'll attempt.
First, the SF does not train for anything remotely close to this scenario. They're trained to infiltrate behind enemy lines and basically off people are quickly as possible. They in fact DO hit targets fairly easily even though things do go wrong- sometimes.
Second, no one ever said that someone legally carrying a pistol could put down the popcorn, draw a pistol, and put a bullet between the bad guys' eyes on the first shot. What I am saying is that it would at least suppress the bad guy and make him take cover or stop firing. While he's doing this, that's more time for people to get the hell out.
In fact, most CCTV footage of legally armed guys taking down shooters involves them using surprise on their side as well. THe bad guy isn't going to identify who exactly is carrying a firearm. Usually they're able to get a direct aim on the shooter without him seeing.
The point of carrying a firearm is not to kill people, it's to make assailants stop what they're doing.
My point is simple: if I had a madman with a firearm between me, my family, and the exit, my odds of getting out are much better with a firearm of my own.