I'm so sorry for your loss @morgs
I'm also really surprised. I've been taking care of a feral colony for a while now and I've never heard of males showing this much aggression towards females. Sometimes tom cats will chase the spayed females if there are intact females and kittens around. They see them as a threat. It's not usually as violent as the fights between two tom cats can be though.
Could you tell us some more about your cat? Was she spayed? Are you sure it was the tom and not another animal that killed her?
I'm also really surprised. I've been taking care of a feral colony for a while now and I've never heard of males showing this much aggression towards females. Sometimes tom cats will chase the spayed females if there are intact females and kittens around. They see them as a threat. It's not usually as violent as the fights between two tom cats can be though.
Could you tell us some more about your cat? Was she spayed? Are you sure it was the tom and not another animal that killed her?