It looks to me like a common public area where skaters are welcome, it's crap resolution, but, if you pause the vid in full screen and look closely, the ledges have pipe for corners, and there is a rainbow rail in the background where the incident takes place. So, taking those things into consideration, now we have a dude just doin his thing in a place where he is advocated to be, and an in attentive mother who can't control her physical anger toward a complete stranger....
I know the skater guy was probably a little taken back by the fact that the kid ran into him, and due to physics, the kid got knocked down, but I'd be damned if some bitch is gonna lay a hand on me like that, that dude was way too passive, that mom had the terminator walk goin on, another thing to note, the mom just casually walked straight to the skater, no checking on her child, no running in panic, just straight up brawler time, she was planning that punch with every step she took, you can see it on her face. Especially after a push like that, and continued pursuit, I would have deflected that punch and sprained her wrist, and yes, then I would have called the 5.0 and shown the vid...
Can someone say cps, cuz ya know if that lady is attacking strangers in public over an accident like that, she most likely hits her kid(s) too...