Was that glass a hair thick? Holy shit that looks like more a building code issue than a police brutality issue.
As for the cop, he lead the perp easily off the train and tried to pin him as usual against the wall to restrain him. The glass was shit so it broke. As you can see he then put him on the ground away from the glass and attended to his wounds. No harm not foul there I would have done the same thing honestly. Though I think the windows were again not up to code.