jack russell terrier is terrorizing cats

by Jacqueline
(FRANCE)

Hi, I have a two year old male Jack Russell called Cory, he's was castrated, quite a while ago, and has grown up with my three cats (I got them all at the same time) but recently, he has started going for them, he won't let them pass infront of him and this morning he ripped the fur out from above one of my cats eyes. I really don't understand why because he's never done anything like this before, he even sleeps with them. May I add that all the cats are also neutered or castrated. Please can you help?