That's all well and good. Excellent advice on the surface.
But no one should get a gun thinking they're going to stop a mass shooting. The odds are astronomical that "a particular person" will ever find him/herself in that position. More likely to be struck by lightening, I'd bet.
Neither should one get a gun thinking they're going to save some innocent. Odds are someone who only shoots a hundred rounds once a month (if that, actually, because shooting all those rounds at an indoor gun range at least is, frankly boring as hell) is going to freeze, going to miss, or analyze the situation wrong and shoot an innocent.
You see the way George Zimmerman's life was ruined? And that was in a stand-your-ground state, most states are not. Orrrr, like Illinois, they wishy-wash with the language so damned much that you can almost bet you will be arrested if you shoot someone with your legal gun unless your story is bulletproof. Pun intended. And civilly? It can ruin your life.
Carrying a gun is an awesome responsibility. Actually pulling it out to shoot someone isn't anything at all like the movies. Your adrenaline is pumping.... your fine motor skills are shot (pun again intended), youre scared ****less, your hand is shaking, you're probably gasping for air... and while you are saying, "Stop, or I'll shoot?" The other guy has shot you in the head.
Carrying a gun is not for amateurs. I know. I am one. I have a CC and choose not to carry. Took all the classes, practiced once a month, bought the $400 liability policy, and then? Realized I would be much better off waiting for lightening to strike than ever have to make a decision to pull the trigger on another human being.
It's not for everyone...
I have a gun in my home. That's enough for me.