I've had a fall out

I have just fallen out with a friend from school, his name is Nathan. We have an school email and he has just sent very abusive message to my best mate (simon) syaing that if he goes near his mates, his girlfriend or him he will kick the S**t out of him. He had also sent a very nasty message to my other best mate (shonagh) saying that if she spreads lies about him again he will fill her face, and told her to go shoot herself. But the thing is she never lied, nathan tried to kiss her but she goes out with simon??? He and his mates made me cry and I feel very upset about it all. The bad thing is I get very angry and I wrote an email back telling him what I think of him, I told him that people only pretend to like him because they feel sorry for him. He even had the cheek to call himself ‘mature’ so I told him that I have seen more mature cheese than him. I said that I dont care about him or his pathetic girlfriend. The closing bit of the email was that if he ever threatens my mates again I will ramm my fist down his throat.

Do you think that I have gone over the top? and what should I do about the whole situation?