I don't think it's cut and dried, that large violent mob was very dangerous, whether or not they shot first. At some point you either give up
and let them have control of the building, and potentially anyone they want to , say, hang by the neck, or you fight back. If the building were
abandoned, then yeah maybe letting the mob have it would be a good move, but if there are people inside still who might be attacked and
beaten or killed, then you have to at some point deter the mob.
In my opinion, having them find and hang Mike Pence would have been poetic justice, but he had fled at some point.