You might not know all the details or back story on this. A teacher doesn't just get fired easily ..
I went into maths class feeling so bad because my maths teacher didn't even do anything and got fired for "pushing and harming children" I was there when it happened, should I do anything?? p.s (the children there are jerks and just make cr*p up for a joke. I know right...
Yes - if you were a witness, they should have interviewed you as part of the investigation.
What country are you in? In America, it's virtually impossible to fire a teacher thanks to unions.