This is a developing story, but current reporting suggests the perpetrator is pathetic loser and 17-y-o right wing militia member Kyle Rittenhouse, who drove across state lines with an AR-15 with the intention of killing people.
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Police on location didn't treat him the way they might've treated eg. a nonviolent vet just standing there, or members of the press trying to report on events; instead, they were amicable, and drove right by him.
Some reports that he has now been charged with murder.