Eh, that's what it looks like from the pic. You could go into the cop's head though.

(I'll be assuming broken leg girl moved aggressively towards the police, for this next part)

Broken leg girl makes some aggressive gesture, police feel backed up to the wall (slightly outnumbered), they take her down. As she comes down, camera girl moves in to probably help broken leg girl, but cop is now on high alert cause he knows he just broke this girl's leg, and people are probably pissed. He's gonna try to fuck anyone up that gets close to him.

After speaking to a cop once, I learned that what's always in the back of their head is "get home." Even if they're doing something normal/fun (like these guys at a tuition hike protest), they're still thinking about getting home. So if you're in a stressful situation, I see it being very possible to overreact by mistake, because your goal is to get home to do the family thing. You're going to do close to anything to achieve your goal, and adrenaline might not let you judge what's an appropriate/according path to get home. For all you know the cop could be GGG, but survival instinct made him Scumbag Steve.

And you can't know some things about him, like is he kinda traumatized about his last rowdy crowd interaction, where someone sucker punched him for no reason. This would make him paranoid and on high alert, leading to unfortunate mistakes being made. Cops should be held to a higher standard, but they're still human beings that can feel pressure in stressful situations. It's difficult to train to be level headed when the shit hits the fan. That's why soldiers try to train as much as possible into reflex/muscle memory. You can't be thinking about where your magazine is when you're being shot at.