I will preface this by informing you that about a week ago we introduced 21 new hens into our flock of 14. We raised the new hens in a big brrode until they where old enough then we moved them into a chicken tractor I built just for a hospital / separation / brooding coop. they where 18 weeks old and over due to become part of the flock. I locked the tractor one day after I let them out and that night went and gathered them up one by one and out them in the main coop, after a couple of days of thsi they figured it out and began going into the coop to be locked up at night. Everything seemed great! Yesterday morning I went to let the chickens out of the coop to free range just like every other morning. I notice that not enough birds come out so I begin investigating. I found 6 of the new brood dead in the coop and in nest boxes. There was blood spattered all over the walls and all the way up to the ceiling (8' tall). none of them where eaten, just their heads pecked horribly. I have my suspicions as to which hen did this. I have a rather large GLW that has seemed like she is asserting her authority with a good deal more force recently, including brutally ripping out feathers behind the comb of some of my older birds, and even after the submit (squaking with eyes clamped shut, head held almost to the ground and NOT running) she feels the need to do a couple of those big full back arch and come down like an axe on top of their poor head, then she starts to walk away and decides that wasn't good enough and goes back for a couple more blows. This hen is the one that picked on all of my girs vents and backs all last winter when I was forced to coop them all up because of a hawk. This particular hen has been excessivly evasive ever since we turned them loose yesterday morning, we tried to catch her to see if she had blood on her beak or head and she will not let us get anywhere near her, it is like she knows she messed up. I took pics of everything, if anyone thinks that this will help me solve my problem? So what do we think? Did I have a predator sneak into my coop somehow or did a hen REALLY kill all those pullets? I have too many hens per SQ FT of floor space, but I knew this, I free range during the day so the coop is only a place to roost. I have a run I am constructing so I can leave the coop door open all the time and just lock the run every night, I suspect if I had this done already I wouldn't be missing 6 pullets right now.