Honestly, this is why people need to learn how to find and use improvised weapons. As humans we've been doing this for thousands of years, other animals do it too. Granted, drinking isn't going to help you think clearly, but shooting after a few isn't smart either. It sure sucks for those who were hurt though, undeserved...
Such incidents make knives seem so much worse, and it's a pity they aren't even allowed to carry such tools in the first place. But criminals will do as they please...
In this scenario, any weapon is going to help. Guns, sticks, sword and shield, anything. But the issue I'm looking at is that when there are 20, and you have the only gun, you can be easily over whelmed. Worst case scenario, I run out and they swarm me, out of bullets they can't shoot me. Not going to rely on that, just a thought.
"Today is victory over yourself of yesterday; tomorrow is your victory over lesser men." - Miyamoto Musashi
[Insert random irrelevant religious quote here]