We had a RIR hen sitting on seven eggs. Last week we found two fully-formed chicks partially hatched, but dead (looked to be smashed) in the nesting box with her. We removed the dead chicks and momma hen continued to sit until she successfully hatched out two beautiful chicks. We moved momma and babies to a chicken tractor so they'd be safe from predators. Everything was going great until this morning when DH went to check on them he found one of the chicks dead in the chicken tractor. It was perfectly healthy the day before but looked to be somewhat smashed when we found her. The other chick appeared fine. Then, this evening I was in the house and heard some very distressed peeping. I went outside to find the last chick lying on the ground hurt. I checked her wings and legs and everything seemed unbroken, but when I would set the chick on her feet she would flop around all over the place. She was obviously hurt and ended up dying in my hands a short time later. I'm assuming now that the momma killed them for some reason, but I can't figure out why. I never witnessed her acting mean to them. She was keeping them warm under her wings, eating with them, doing everything that a good momma hen is supposed to do. Has anyone ever had a hen kill her chicks for no obvious reason? Also, we have another RIR sitting on some eggs. They're due to hatch on the 18th. I'm a little nervous now about leaving those chicks (Lord willing we'll get some!) with the momma. If you were in our place would you go ahead and leave the new chicks with the hen or would you remove them to a broody pen once they're hatched? Thanks for any advice you could share!