And what would those gun owners in defensive positions have done if an undercover cop or other gun-toting citizen come down their aisle? Probably shot them down.
There's no good solution. No guns won't happen, all guns is no panacea. Look around you the next time you go anywhere and imagine most of the people you see toting pistols LOL...yeah, that'll end well the next time a shooting breaks out in a dark location like a theater. Or a sunny location for that matter.
As long as we collectively continue to go insane, more of us will die. Better get used to it, or maybe see if there's a way to help more people before it comes down to a shooting. You'll never stop all of them, but seems like prevention is always better than curing. But as we see with the War on Drugs (tm), this country isn't very interested in investing in prevention. (in that case, they much prefer investing in the private prison industry).