In my experience, roosters tend to stay nice (to us people) for longer if they have been raised by us from an egg onward. So roosters that were given to us as adults for various reasons, they were more likely to turn mean earlier on. The last rooster that we were forced to enjoy in a gravy was 2 years old. He was extremely nice up til the sneak attack on me from behind. I now have a renewed sense of healthy fear. I do not turn my back on any of our roosters (there are 3, each over a flock). I also observe that an individual rooster will sometimes start to show aggression toward my husband first, sometimes just little signs. I pay attention, because it seems that once a rooster begins this, he will eventually become aggressive in general even if he is still being super nice to the rest of the family presently. They always start with my husband. He spends less time in the pens. Maybe that is why, I'm not sure. I hope you are able to be at peace with whatever happens to your guy.