It will be quite interesting if/when we find out what happens to the third cop and what that cop’s role was.
I’d guess that the tazer cop is in the clear. From his vantage point, he has to assist the officer who is trying to make an arrest (good or bad arrest doesn’t matter) and who might be in peril once he disappears from view inside the apartment door. Tazing the kid helps get the kid down on the ground, complete the arrest (again, good or bad arrest doesn’t matter), and diffuse a dicey situation.
I personally would discipline the nightstick officer. The kid is down on the ground and subdued at that point. That force wasn’t necessary. But nightstick cop might be excused for similar reasons as tazer cop was given that his actions occur over the course of just a few seconds.
As noted above, I think the cop at the door was mostly acting within the law given the open doorway and given that he’s trying to make an arrest. I also think he showed significant patience while the drunk kids belligerantly screamed out their moronic legal theories and kept escalating their behavior. But I would fault him for not showing even MORE patience, even though his legal grounds were solid.
My guess is that the door cop is the one who is still being investigated given his primary actor role in the incident.