Maybe he's just trying to give her a warning, or tell her to stay away from this particular park from now on, or anything that wasn't 'you're under arrest'. That's the thought process that makes her stop and turn around when she hears the officer call after her.

It takes her a moment to realize that he's not saying any of the things she'd imagined he would, and she even looks a little confused for a beat. "People... are protective of their children. He was probably right to be angry at me."