Chickens can be cannibalistic. It's not your fault the chick got out. I usually move my chicks into the coop when they are 6-7 weeks old, then they are closer in size. Hens are very aggressive and will pick on newcomers. That's why you don't just move them right in. I actually had my hens pluck all of the feathers off a 6 week old pullet that one of my hens had raised.
Can the hens see the chicks through a fence or such?
Can the hens see the chicks through a fence or such?