Help - Blood in the coop and on different chicks

[vweers]

I think I have an aggressive chicken not entirely sure who but have my suspicions. IT might be the one I think is a male but not positive. WE don't have a run in quite yet but I do let them roam. They are about 7 to 10 weeks old. I have about three ages. They have been together the entire time. Not sure if this is pecking order or just plain meanness from one. Any ideas of how to tell and what to do? If it is the one that I think is the male then I will just rehome that one. I have three (my three EE"s) that tend to be rather aggressive so it could have been one of the others too. Or do I need to just watch and see what happens.