I know you won't get this, but someone with the mentality of walking around armed concealed in public and willing to shoot someone, is called a bad gun culture. When someone's brain with a gun would use that gun on someone, they're an unsuitable gun candidate.
The two errors in America's guns -
1) The culture; people's orientation towards guns, towards others, and where's safe to store and use them
2) Gun accessibility and their features
At the moment, the emphasis has been more guns, more armed citizens, and a greater push to get any restriction, pardon the pun, shot down. And what's the result? Weekly mass shootings where 4 or more are injured and/or killed.
And this mass killing took an armed cop and not this fallacy of an armed citizen. Proven fact.