There’s other video that shows the beginning of the altercation. He is trying to get closer to the front, and some person starts pushing him away. He tries to go around, and the person puts an elbow to his face. He grabs the person’s arm and throws them down.
Then people start screaming at him, so he leaves. That’s when we see the next video, he is walking away, and a guy shouts “I’ll kill you” and runs up and tackles him and beats him with the skateboard, at which point he shoots the guy beating him.
He may have been one of their own.
Do you have a link to that video?