Any charge requires mens rea. If he was attacked, there is none. There was no criminal intent on Z’ s part. If I understand correctly, he was in the LEO academy. I still don’t sit in a restaurant with back to the door since then. Identifying criminal behavior is instilled during those three months to the point of paranoia. All cops or potential cops are taught this.
I think it was the citizens academy, which is more of a “and this is our jail where the bad people get locked up” sort of thing.