Explain why no one ducked immediately after “a girl was shot”
Because with only one shot, almost everyone is trying to figure out what happened, and why?
That is the way the real world works.
With only one shot, no one knows immediately if someone was hit, if it was an accidental discharge, if someone is wounded, how bad it may be.
It takes time to process and figure things out.
This was the one shot fired in the whole Capitol protest.
There was only one shot fired and after that it was over. As to why they didn't duck, most of them were surprised. If more shots were fired, they would have ducked or gotten out of the way.
When people are actually in high stress or crisis situations, they quite often do not act rationally or in textbook fashion as people reviewing it after the fact think they should. After she was shot, the Antifa types stopped trying to break through the door and started acting like innocent bystanders which they clearly were not. They like being bullies until the consequences become real.
They are not "crisis actors". They are professional protesters, trained and prepared to treat riots as a game where they play their parts. When they see the police are crossing over into making arrests or using lethal force, they stop playing the game and go "who me?"
When working as a security guard, I saw this during the protests after Michael Brown was killed. One particularly obnoxious person wanted to play the game with me until I backed off and started making calls on my cellphone. When he saw I had enough and was now taking action, he stopped being a loud mouth, and quickly and quietly left.