"Bear spray" is an extra potent version of pepper spray. It's a potent irritant but that Sicknick phoned his family from his office and told them he was OK basically proves the "bear spray" was not the cause of his death. Neither are within the ability of someone suffering respiratory distress.
IF one of the rioters used bear spray against a human, that would be assault, but not assault with a deadly weapon. So if you want an indicator of how much the prosecutions will be politicized, watch how this guy is charged, if he exists. Anything more serious than assault and similar riot-related charges means politicization and an attempt to intimidate the guy into pleading guilty to a lesser charge.
That assumes he didn't use the 5.56 mm wild-pig-exploding bear spray.