In the very scene where the girl got shot, if you look from a different angle, you see there were a dozen riot police behind them doing basically nothing [0]. I have yet to find a satisfying explanation for it, considering the protesters were literally smashing doors and windows. [1]
And, let's be frank here: people were protesting the police, and the police took it personally. They felt threatened.
I have personally witnessed police brutality in my community. Have you?
To say that the police felt threatened by protests aimed at the police, and that because of that, the police acted more brutally than they otherwise might have, is not a justification of police brutality. It is an explanation.
That's the relevant point, not whether or not the cops removed the barrier. The cops knew that hundreds of protesters were planning in on breaking into the capital building to assassinate senators, and purposely didn't send anyone to stop them. The whole thing was literally planned in public on social media.