Well............the scenerio depends on exactly what State/ locality this episode unfolded in. Call 911, tell them who you are, and you're in the process of whitnessing a possible ADW and possible Homicide...........I could be wrong in my thought train with what I'm about to say in my reply, but it's how I feel I'd handle it..
Personally, even in the state of Ma..............a ADW is considered a "shod foot"........sooo ith that in mind, and watching the altercation unfold, I would have waited til the guy got struck with the skate board.. Based upon the phyisical events that are unfolding, I then would have taken a stand, with my own safety in mind, and the victim's safety as well.........and drew my weapon and ordered the assailant to halt..(now.....you already know he's struck and possibly critically/ fatally injured the victim........and who may be the next victim?? take a guess.......especially if I'm attempting to protect the victim.. BTW......the guy should have never hit the skater's hat and knocked it off...........AND the skater could have walked away without becoming the agressor or not even striking the guy with the board..
The fact is the skater continued, and at that point HE has become the agressor.........I then would have again ordered him to halt.........pointing my weapon his way, and attempting to get between him and the victim...........If the skater came at me.......and attempted the strike me........with what I deemed as the DEADLY WEAPON that he has in hand (the board) acting in a threatning manner, and attempting to cause me bodily harm, I then would have dropped him .. As for the rest..............I don't think they would have continued.........as now they knew EXACTLY what is about to happen, should they become the agressors..
NOT a "cowboy " here, just running some thoughts through my cranium.