If my (only) firearm is in my car and I can get to my car, chances are I will not be going back into the threat zone.
Yep, the popo are going to expect it to be gun free and we have already established about 99% of the folks with guns shoot first and ask questions later, so no way in hell would I be hanging around.
When I despair, I remember that all through history the ways of truth and love have always won. There have been tyrants, and murderers, and for a time they can seem invincible, but in the end they always fall. Think of it--always.