Wow. I like how you responded. It looks like I jumped to a conclusion. For that, I am sorry.
Anyway, without further information, just based on the detail in the scenarios you have laid out, I would not draw. Depending on my position, I would either turn strong side away from the robber (if I am close, I don't want to motivate him to get any stupider than having drawn), and (if I can do so without drawing attention) I will put my hand on my firearm and deactivate retention, or I would immediately move to cover and concealment. Most robbers, even if the brandish, will not shoot. I don't want any actions I take to cause the shooting to start. The teller has been trained and tested. He or she knows exactly what to do to get the robber and his gun out the door. And that is the goal, getting him out.
The only way I'd draw is if I intended to shoot. That will only happen if the shooting has started or I am absolutely it is imminent. In that case, my priorities are (1) protecting my family members, (2) protecting me, (3) protecting friends, and (4) protecting other innocents. In fact, (4) is so far down on the list, I will only do (4) if I can do so at zero further risk to (1), (2), and (3). I am not a policeman, and I feel no duty to risk me and mine for others. I may choose to do so, but that is my choice.
I hope no other carriers in a bank during a robbery feel the need to be proactive. Let the bank handle it. They know what they are doing. Draw and fire ONLY if the shooting has already started of you are 100% sure (I don't know how you could be) that shooting is imminent.