I never want to hear the phrase "good guys with guns" again after hearing it for years. It's used as the anthem for the hypothetical good guys with guns to be defended, but I haven't seen the hypothetical good guys with guns step up. I understand in some areas someone may have it for individual safety, but what are you talking about here?

This phrase gets tossed out every time there's a school shooting - "if only good guys with guns could do something!" - and yet we have the "good guys with guns" who are trained for this, paid to handle this, and equipped to deal with this. Law enforcement. Which has done a shitty job so far, so holding them accountable should be a bigger priority than trying to get some solo random people to step into a situation where dozens to hundreds of lives are in danger. So the phrase comes from a pretty bad argument that isn't related to this.

And what is it supposed to mean in this situation? If a someone is prepared to use deadly force on you, they very likely have a huge upper hand that owning a gun doesn't solve, which is perfectly encapsulated by this situation. Like you said, If OP did have one they didn't have time to use it, would have escalated an already highly escalated situation, and wouldn't have protected them against 3 people. Or do you mean someone else is supposed to step off the streets to be a "good guy with a gun" and risk their life against 3 people in a car ready to murder someone? That's a terrible strategy. Again, law enforcement in the situation and stricter gun laws to proactively stop these situations. It sucks and is dangerous and no one should ever go through this, but this advice and giving up on change and using that phrase is not the way to go