It was supposed to and did.
Break out your crayon and follow along. If the shooter kills himself, the other "good guy" with the gun becomes a moot point.
But they don't right away, so it doesn't make sense. You broke your crayon. You can stand there and pee if it happens to you but not everyone wants to be put in that position. And fortunately have the Constitution on our side.
And response doesn't happen right away either regardless of the John Wayne fantasies you guys have.
Yes the Constitution is on "your" side. That is why this will never be resolved. A zillion decades from now, we'll still have thousands of needless deaths that no other developed nation has and you guys will still be claiming it's not because of guns when the access to guns is the ONLY difference in the nations.
Until you account for differences in cultural mixes, you can't make that statement honestly.
London doesn't have cultural mixes?
Sydney doesn't have cultural mixes?
Tokyo doesn't have cultural mixes?
Paris doesn't have cultural mixes?
Egypt doesn't have cultural mixes?
Helsinki doesn't have cultural mixes?
Madrid doesn't have cultural mixes?
Lisbon doesn't have cultural mixes?
Berlin doesn't have cultural mixes?
There are ghettos and slums in every major city on earth. We have the same media, same books, same video games, but different gun laws.
It's the only X factor.