Tactical Scenario-Robbery Gone Bad

In the video below, two armed robbers storm a convenience store and attempt to rob the place.  There is one customer and two clerks.  While robbing the store and demanding money, the clerk plays stupid and claims to not speak English.  That sends the robbers into a rage and they start killing everyone.  Now let me set the scenario.  You are ordered to the ground before you get a chance to blink.  The shotgun wielding robber is yelling at the clerk and suddenly shoots him.  You are carrying concealed. What do you do?

 

I would hope that I immediately break leather and commence to initiate a skillful gunfight taking out both robbers without sustaining a single wound.  That would most likely not be the case.  This is nasty.  This scenario is probably one of the biggest "odds stacked against you" scenarios you could face.  I am not one of those guys who assume he would do all the right things, but in this case I would need to in order to come out on top.  Obviously, the ideal would be to see them coming in and take some action then, but that is not the scenario. Enjoy.