Another neat tip from Masaad Ayoob was from his Judicious Use of Lethal Force video. It was during a talk about home invasions, but it applies here. If an altercation is imminent, and you draw your weapon to a low ready or whatever your training describes as a ready defensive position, and the BG continues to attack...You can make some assumptions.
1) He knows that I have a deadly weapon in my hand because he can see it.
2) He can reasonably assume that I know how to use it and that it is not an empty threat.
3) I don't know anything about this person. He may be a thug, a retired Navy Seal, SAS, KGB, Honor roll student, etc.
4) In that situation I know nothing about what training he has, but he knows something about the training I have.
5) No one would continue to attack if they thought they had a major chance of losing.
6) Because the bad guy is pushing the attack he must be confident enough in his skills that he can still win the altercation even with me holding a gun.
7) He has enough training to win the attack unarmed against an armed gunman
8) The only way to stop him is to kill him.
My thoughts... exactly.