The point I would like to make, after watching a few times, is that he says he needed to punch her like that so subdue her, yet at least two of the other officers seem to be standing (one kneeling) watching it happen .. if she was really putting up such a violent struggle at that point, why were they all not holding her down or helping to restrain her? My totally personal opinion is, she hurt him and he reacted by hurting her back.