In my CCW class we were instructed that IF we decide to draw and cover, we loudly tell the BG to cease his behavior that caused you to draw (think "Demolition Man"). That way if you do put them down, witnesses can attest that you drew as last resort and gave them opportunity to withdraw. So in this scenario if you draw and de-escalate, there wouldn't be any charges filed against you. That's how it was explained to me, hope I never have to prove the theory.
So many threads, so little time and I have an opinion on EVERYTHING!! It's just not worth anything....