Okay, let's say an armed citizen is inside the doorway of a convenience store, pizza parlor, bank or similar robbery target when they observe a person approaching the door wearing some type of mask to conceal their face and carrying what clearly appears to be a firearm in their hand. The potential threat will be coming through the door in moments. Assuming that both the mask and the carrying of a firearm in hand are both inappropriate for the circumstances, what can the armed citizen do at this point? I'm interested more in the legal aspects of what the armed citizen can do, rather than the tactical considerations. Can the fact that the approaching person is wearing a mask and carrying a gun establish jeopardy even though that person hasn't directly threatened anyone yet?