Watching that video, it's clear that the other protesters saw the firearm and were shouting warnings while backing away from the doors for the most part. I'd say the officer clearly wasn't situationally aware and paying attention to his surroundings any more than to proper use-of-force rules. The officer gave no warning, and that the other protesters saying "He's got a gun" and the like are meaningless in this situation. It is incumbent on the federal officer to give a warning and try less than lethal resolution before resorting to deadly force. The Capitol Police officer is clearly not performing his duties as required and should be held accountable for his misactions.