I'm sorry that this is happening. I know that Bichon Frise are never supposed to show any kind of agression. Perhaps something else could be bothering him? Could it be physical? Also I know that there might be some little behaviour thing of yours or of another family member that could be causing him to do this. It is very hard to tell without seeing it. Is there any way you could upload a video so we can see? Sometimes it is the littlelest thing that is setting the dog off.