Just a guess: BLM supporters mad at the Rittenhouse verdict retaliate by attacking a parade that would probably attract conservative-minded people because of the Holiday theme.
As I understand it, Waukesha County is to the west of Milwaukee, is heavily Republican and voted for Trump. I have no idea if any of this or the trial have to do with this atrocity (pray to God for the health of the victims) but the facts and video released so far seem to indicate that something vicious happened there tonight.
Waukesha County 60% Trump 40% Brandon.
Well, the president did say that anger is the correct response to the verdict, so here you go. The perps were just following his lead. (Assuming the act was intentional and as it seems, etc.)