I had a RIR roo that did this to our Buffs. Once the targeted Buffs were removed from the coop, he turned on my son and me. We *think* it was because I was pregnant at the time and he was jealous. I know that sounds crazy, but it's the only thing we can think of. Shortly after our son was born, the roo became extremely aggressive and seriously attacked me. I was genuinely afraid of him and my son was terrified. We dispatched of the bird.
Please keep bacitracin on your hen's wounds and keep them covered in gauze for a few days. I had three hens with very serious, life threatening even, wounds from a dog attack and they all survived. They just need good care.
Let us know what happens with your roo and your hen.