I found this info on "rapist roosters":
"Then there are other genetic problems that no one understands. One of the worst cases was the rapist roosters. I wrote about them in Animals in Translation. Fortunately, the broiler industry has made some genetic changes to correct these problems, although there’s still a way to go. The rapist roosters violently attack hens and injure and even kill them. Before the 1990s there weren’t any rapist roosters. They just suddenly appeared out of the blue. First it was just one strain of roosters that had become aggressive but within a couple of years almost all strains had developed the same behavior. Nobody knows why.
The rapist roosters have two problems: They are hyperaggressive and they have stopped doing the courtship dance the hen needs to see before she will mate. They’ve lost the little piece of genetic code that makes them do the dance. When the hens don’t see the courtship dance, they don’t become sexually, which may make the roosters’ aggression worse. An unreceptive hen would be a form of frustration because it is a restraint on the rooster’s action. So the RAGE system would be activated to some degree.
When I wrote Animals in Translation it looked like the rapist roosters were a side effect of the industry’s selective breeding program to create chickens with bigger breasts for more white meat. But now researchers aren’t sure what caused it, or whether the hyper-aggression and the bad courtship behavior are the same problem or two different problems that happened at the same time. Industry breeding programs are trade secrets. It’s obvious the industry is selectively breeding for larger breast size because breast size is getting larger. But we don’t know what other selective breeding programs the industry might be using."
He may be trying to mate, but he kills them in the process.