school bullies

Right after I wrote my last post about my son and his recent aggressive behavior I went to his school to pick him up and saw this child push and hit him! And then I remembered my mom telling me that this particular boy is very rough and aggressive, hitting, pushing etc... So I'm trying to put two and two together and I understand I just witnessed one situation only but still it seems like since my son is seeing this behaviour in his classmate he may be following the same... Anyway I told him to stop this kid from doing it next time and complaining to the teacher. And I'm going to have a word with the teacher too on monday... I am also reinforcing in my son that this behavior of this boy is wrong etc so he realizes that he should not copy it... Anyway again I know one random incident I witnessed, maybe I'm making too big a deal of it and I know there r bullies in school but let's see if I can put a stop to this...