If you put a hand on a cop, you do deserve to get roughed up a little.
I'm shocked this cop couldn't get her on the ground.
Also, his ass was slipping. The kid came in and shrugged - he was right behind the cop and could have easily pulled that gun free.
That cop, IMO, just isn't good enough at his job. Put him on a desk or send him back to traffic dept for 2 years.