He forced his way in and got into a physical altercation with the homeowners?
No kidding... First congrats OP on keeping your cool, kudos to your girlfriend for her instincts I have to admit. I'm not a gun owner and don't really believe in it mainly because I never want an unfortunate accident to happen with my children. But I can say, if I was and that dude took one step towards my girls that barrel would've been resting firmly against his head.