At what moment did the cops start beating innocent students?

Pardon me, I am not in India right now and haven’t been getting unbiased reporting.

If any of you went to the protest can you tell me if the police marched towards the protestors and started beating them or the beating started after (if) the protestors tried to cross the barricades?

I am extremely overwhelmed looking at the videos, any student who didn’t break any rules and still got beaten should sue the Delhi police!