first of all, and for the record - anarchy should be our system and cops (as we know them) shouldn't exist. but thats off topic and we dont need to get into that.
having said that,
I do think this police officer is the type to escalate situations unnecessarily (as is the kid obviously).
BUT once the kid attacks the cop, I don't think you can entirely fault the cop for shooting him. I do think you can fault the cop for the way he handled the situation up until then, but hes not responsible for the shooting itself (based on that bodycam).
If you attack a cop you might get shot. Doesn't matter if hes being a jackboot thug and throwing his weight around. is it right? doesnt matter.
The only other aspect to this is whether being quasi-tased is enough to completely trigger fight-or-flight and thus the kid isn't in control of his response - which I dont know the answer to either way.