Not if this is the first time. I would think if you have tried all other measures such as talking to the other childs parent, Getting a Teacher involved if it is happening at school. If they go to the same school how about getting the Guidance Counselor involved. My aunt is a Guidance Counselor they deal with this stuff all the time.
Verbally.....Ugh No, you would get laughed right out of there unless it was sexual or a death threat. Go to the parents, if that doesn't work, teach your child appropriate coping and minimize contact between the two.
verbal assault probably isn't a punishable crime but the fact that he's allowed to run amuck like some 18th century street urchin is. Call CPS or the police and have someone be held responsible for his inappropriate behavior.