Got home from work this evening, and read the school communication book.
Teacher wrote that DS (asd, 5) has pushed another child and the child hurt badly his head. 
DH who hadn't read the book didn't know anything about it, as DS never mentioned it (wouldn't really expect him to tbh)
Apparently it started as play fighting then adult intervened and told them to stop, but DS didn't stop, he was told several times but kept on and the incident happened.
I'm sure he hadn't meant to do it, as he isn't usually violent but he can get overly excited and will harrass other children without being aware when they have had enough, and he doesn't get very well that he can hurt others.
DD is often on the receiving end of his pushing and pulling, but he always feels sorry afterwards when he sees her crying.
The trouble is, when he is having one of his hyper excited moments, he won't stop when we tell him to, and he has to be sent away to the step or his room for some quiet time just so he can calm down.
I hope the child is ok.
Not sure if i should write anything back in his communication book about the incident...???