Rooster trying to mate/hurt other chickens? What to do??

[Pukkits]

Chickens have a survival part of their brain that is rather primitive. If there aren't perceived to be enough resources, it causes a lot of stress leading to destructive behaviors and often illness. It's not uncommon for chickens to try to kill other chickens to give themselves more space, food, or for roosters hens to mate with, to eliminate the competition. This is why it's so important for chickens to have adequate space in a coop/house and run.