Actually Perp-3 wasn't violent, as far as I could tell from the story. I think he mainly called him "perpetrator" because he was close, stood around, didn't do anything and seemed to be okay with what happened.

And of the other two, Perp-1 seemed to have been the manager, while Perp-2 was a customer (judging by the shades in his hair, and the "meal" in front of him).

I'm guessing the customer felt paranoid from the camera and complained to the manager.