He did the wrong thing, no doubt about that. He had a flash of temper. But she started it, She is the one who slammed the cell door, striking him in the face and probably hurting him quite a bit.

Would you expect her to be charged with that? I bet she wouldn't be. That sort of behaviour would be par for the course with a lot of these types of young ones.She would claim 'accident' and the police officer would be expected to take it.

Attempted robbery is not the same thing as attempted theft, by the way. It is a much more serious charge, usually involving violence or weapons.

This officer's main mistake was to give the girl the slightest bit of leeway at the start. That door should have been shut and locked from the first and if that meant no cool breeze or fresh air for her, so be it. 

He should not have lost his temper. I'd say he was trying to make her sit down and get out of the way so he could lock the door. It should already have been locked.

But the thing is here, what i used to say to some students when I was teaching and they came to me complaining about being hit. Often the story came out that they had struck the other child first, so i would say-What did you expect to happen? Their reply was always-but it is against the rules for them to kick/hit me or whatever. So it was, but I always pointed out that if they hit someone first, there was always the risk that the person would hit back.

Police are human and most people have a snapping point, I would say he went too far but as a result of having his initial kindness repaid by a metal slap in the face. As for the girl, one of life's lessons should be that actions have consequences.

If he faces a heavy fine for his actions, i hope she faces a heavy sentence for robbery.