I have only heard of it a couple times before. I was appalled when my little pullet did it. She was only a couple weeks old and did the same thing...pecked another chick's head until it died. I think it was kinda accidental tho. It made a mark that bled and the red made her just keep pecking til it was too much. It was pretty gruesome to discover that the next morning, when the day before the chick that died just had a tiny bloody mark on it. I hope that's not what's happening with yours. It's a really sad thing to have to deal with.Yikes! You too? I'd never heard of this before.