Hi Diane A, and welcome. I'm sorry to hear about the problems with your cockerel. As Foxy says, once they develop that sort of behaviour its hard to change their mindset. You do need to think hard about what to do with him, as if he attacks someone who is not prepared, he can cause serious damage, for which you would be liable. Also, an attack would be very frightening, especially if a child was involved. There are various tactics people have tried, such as getting hold of him (how?) and holding him head downwards for several minutes, to impress your dominance on him, though even if you make him realise you are the boss, he may not think other people are also! I have heard of people going into the run holding a dustbin lid in front of them to protect themselves, but as he's free range this wouldn't be much off an option, would it? Also, not very relaxing.
Maybe he just doesn't know when he's well off. There are so many nice- natured birds out there, it makes you wonder whether you really want to keep one which is dangerous and frightening to people on your property.