You sound as if you are ready to blame the teacher [aide] when you do not know anything whatsoever about what actually occurred between the teacher [aide] and the student.
What is that all about? Kinda jumping to conclusions, aren't you?
Why do you think she was mean to him? You don't know that.
And, even if she was - he shouldn't have done what he did.
Without actually knowing what happened, I imagine it was probably something simple like - he wanted to continue playing with the video game machine (no-doubt owned by the school) - she knew his time was up and he needed to get to his next class - something like that - whatever - we do not know - but, she probably had a good reason to take it away from him.
(Now, if the thing really was his property - then, yes - that does introduce a whole new aspect to it. In which case, she should not have acted alone; but rather, gone to "higher authority" in the school system and let them handle it.
Still, what he did was not right for him to do.)
What I do know is - in 17 years, he should have been taught:
~ that he must respect others
~ he cannot always get/have what he wants
~ he must be able to accept direction from others who guide him
~ he has to exercise self-discipline in order to get along with others
~ etc. (many other things also)
It does not matter how [much] "special needs" he is...
Part of the "blame" for this incident rests upon:
~ the 17-year old
~ his parents/guardians
~ the 'community' of people that shaped his life as he grew up
~ (you get the idea - if you want to blame, spread-it-out to all of the several places where it belongs)
This is a complex situation. And, there is not a single "fault" with a single individual. There are many "faults" that played into this event.
We need not be "judge, jury, and executioner" without knowing a whole lot more about this situation than we presently know.
Yes - it is even possible that the teacher [aide] did something not-the-best in this situation. However,
the highest likely single general thing we might postulate about this entire scenario is that the teacher [aide] did no wrong - certainly not sufficient to invite an attack like what played out on the video.