You have a Hen Killer Rooster on your hands, they will kill them for pure spite. These type of rooster need to be cull on the spot otherwise their offspring will continue killing hensLong story short, we have two flocks. Never had an issue with one, but the rooster in the other flock has killed three hens.
The first time was a few months ago. He killed one and we thought it may have been an accident but then he killed another one shortly after. So we isolated him for a while. We recently got new coops and figured maybe he could be integrated back into the flock of hens since we are finally in fall and it’s been a while. I also read a few things on here saying to isolate them and put them back to prevent killing. But one day later, he killed another and we have him back in isolation. The thing is, I barely ever see him mate with them. So I’m pretty sure he is doing it out of pure aggression. Maybe I’m wrong.