That shooter was an Asian man who apparently was there to protest the Milo appearance.
He said he thought he was being attacked by a "Neo-Nazi Skinhead" when he fired on his assailant. There are at least two videos which clearly show the incident.
He was definitely under attack when he fired, and the police never charged him with anything. They never charged his assailant either. Things that make you go "Hmmmm".
I believe that incident was a "Blue-on-Blue" casualty.