I'm laughing my ass off at his predicament, but honestly if the whole basis of the agg assault charge is booting the canister back in their direction, and them all wearing masks, it's kind of an major overcharge and it'll most likely end with him pleading out to a misdemeanor.
He may also have thrown one back. I don't know if that makes much difference, though. PHX has a D Mayor, and (IIRC) voted against Sheriff Arpaio, even in elections he won. So I suspect the DA and local prosecutor's off will be at least some what liberal and sympathetic.
Over-charging seems to have become a tactic for some prosecutors, using the cost of defending oneself as leverage to get a plea to a lesser charge. At least, in this case, if this moron pleas down to a misdemeanor he'll have a criminal record and have to choose between admitting it on job applications (and a subsequent explanation) or lying about it (which could be grounds for being fired).