It's the wiry ones you have to watch out for. But this big guy caught his opponet with his skates on and managed to kill him. I'd vote involuntary manslaughter.
Yes it is the wirey ones. Smaller guys who like to pick issues with bigger guys are called giant killers. It's usually a win/win for the little guy. If he wins fairly he's top dog. If he hits the big guy with a stick then it's ok because the other guy is too big. On the other hand if the big guy wins then he's victimizing a "little guy".
In this instance, I'm not sure but I would opt for involuntary manslaughter at worst.