Response to BillCA
Physical contact may be the necessary tactic, at that point, but remember that away isn't the only direction, and may or may not be the best direction. Deflecting his gun hand to inside or outside also allows the opportunity to move IN, if you can pull it off.
Years of training in aikido mean my first reflex is to move in on an attack, and get inside and to the rear/flank. It really messes with an attacker's head when you close the gap, with melee weapons or open hand. I'd imagine it could upset their game plan if a gun were involved, too.
Of course, it helps if one practices drawing while moving.