Better safe than sorry. You identified a possible threat (four of them in this case) and you chose to avoid any confrontation. Our goals should always be: AVOIDANCE, DETERRENCE, and DE-ESCALATION (in sequence of importance). If you are able to meet the first goal there is no longer any need to meet the other two.
Could they have been actual threats? Quite possibly. Should you have waited to find out? Heck no!! Could you have been a little too paranoid? Who cares? Just because you're paranoid it doesn't mean that they weren't out to get you!!
Had they gotten any closer would you have been justified in using lethal force? It all depends. The disparity of force is with them because they had you outnumbered. But even then, you had to be in fear of death or grevious bodily harm before you can use lethal force. However, the fact that you were with your girlfriend might be enough cause to think that they could have been targetting her even if it meant having to go through you.
Regardless of State code, since this is not your home (Castle Doctrine), I don't believe you have the legal recourse to stand and fight if you had the option and ability to run away. What would have been your purpose for standing your ground when you could have easily escaped (as you did)?
Just because you have a gun, it doesn't mean that you can use it to selve every problem you run into, does it? JM2CW.
NOTE: I am not a lawyer nor do I play one on the internet.
