Unfortunately, that has a high chance of happening.
It's understandable if someone wants to try to intervene and help people, but if you have a gun in your hand the police (or other wannabe hero bystanders) have ZERO way of knowing you aren't the bad guy and they have no time to pause and decide first.
Wannabe heroes are better off acting in helping guide others out of there and see them to safety. Let the cops take down the bad guy.
I'd rather be a dead good guy with a gun who went down fighting than a dead good guy without a gun who get executed by an urban person without putting up a fight.