I have a huge Roo and he is sweet as can be, but I also know that he is not a human therefore cannot reason. He and I have a mutual respect for one another and I know what he is capable of should the mood strike him. I never go out there that I dont have a backup plan which is a squirt bottle and a "just in case" treat. Should he ever decide to be aggressive, I will spray then treat, then attempt at re-homing him, as he is a good Roo with the hens. Im sad to think that someone would take it upon themselves to kill a Rooster without looking for resolve, and someone elses Roo, unthinkable. Were there any attempts on your part to notify his owner about his prior behavior? Its about a lot more than a Rooster who is ornery.