Here's a great "comic" by Jen Sorensen that would be funnier if it wasn't so disturbingly true.
l've been thinking in much the same way about what would happen if the NRA's wet dream became reality, and the United States was filled with people carrying military-style assault rifles and other guns openly around in public.
That'd be great for mass shooters. Blend right in.
Start shooting in a mall, kill a few people, then run around a corner with your rifle over your shoulder and start yelling, "Oh, my God! There's a shooter back there! Take cover. I'm going to move on and keep warning other people."
When everybody is carrying a gun, there will be no way to tell the "good guys" and "bad guys" apart. Until it is too late. Well, unless would-be mass murderers wear t-shirts like the one shown in the comic.
(But would they tell the truth and check "evil" if they actually are evil?)