There are just too many variables for there to be ONE right answer. As far as rendering aid, I dialed 911, that's all the aid the SOB is getting from me.
As for everythihg else, you just have to make the best decision you can considering the "totality of circumstances". Is the BG mobile? Well what did you shoot him WITH? a 22 or a 12ga slug? If you hit him with a 22 that only went through the muscle, he may still be VERY mobile, if you broke his femur with a 12ga slug, he ain't likely to be going anywhere. If you cut his femorial artery, he's going to bleed out real fast, go into shock and possibly die. The BG himself is a MAJOR variable. There are cases of people who dropped DRT from wounds that theoretically should not have been leathal. There are the cases of guys with multiple leathal wounds killing the guy who shot them. Your spouse/SO or other household members are a variable. They may be better than you are at dealing with the situation, you might want to let THEM take the lead.
IMHO, you priorities should be;
1. Keep YOU alive an safe FIRST. You can't protect anyone if you're dead.
2. keep your family safe. Retreat and laager up, or evacuate.