If the child thinks it’s funny to tease or push another child, there is intent — and given that she was physically injured, there is power. Bulling doesn’t just magically start one day in 8th grade. Given that the parents care enough to a) not assume their precious child wouldn’t do this, and b) meet with the school — -I feel reasonably certain they are modeling empathy and other good behavior.
Kids are kids and they do not always make good decisions. That said, I am thrilled to see parents taking the problem seriously. However, don’t confuse taking it seriously (addressing it at home and at school) with overreacting. 5 year olds make poor decisions, but it doesn’t mean he will continue to do so once the issue is addressed.