The threat was the mob at the last barrier between it and the sheltered members of the government, and she was at the very head of the mob pounding to break through. Whether she personally and individually was a threat is a distraction. She personally and individually was in the lead of a violent mob the officer was charged with stopping. Until then the Capitol Police had held their fire, absorbing the violence at their physical expense. That tolerance was no longer affordable. At the sound of the gunshot reverberating in the hallway followed by the sight of one of their members sprawled on the floor, the mob's assault ended in its tracks. The officer deserved a medal and Trump would have awarded him if this had been a BLM riot he stopped.