Not I.Posted by sjohn26: But at 1st sign of ANY weapon (a ball-point pen held in a menacing manner counts) I would drop him/her/it.
First, most robbers these days do display a weapon. Second, most robbers do not use the weapon except to intimidate--unless they have to. Third, there is a high likelihood that the robber is not alone, and that one cannot tell who his accomplice is by looking at him--unless something causes him to spring into action.
So, unless there are strong indications that the robber is about to start shooting without provocation, I would choose to not (1) start a gunfight that would likly not have happened but for my intervention; (2) risk being shot by the tail gunner; and/or put innocent persons at risk by shooting in a confined area full of people.