Dead chicken for no apparent reason.

[texas kat]

I have lost three chickens in a week. the first time they were all out free ranging and when I got back my one auracana was dead in the cage and the other one was gone. Then one week later, my RIR chicken was dead in the cage with the door shut. no one seemed to acting strangely before the incidents. I only have one left but have five chicks in another place. is this a disease thing or an animal? none of them had marks on them or any blood that I could see.
thanks.

 

[TeamChaos]

How old are these chickens? I'm confused- when you say they are out free ranging, I imagine that meaning they are turned out of a cage to forage, but you mention that you found them dead in a cage- are they going back in on their own?