Something is killing my bantams

[tpsisct]

I have an intruder in my barn I raise bantams in my barn and the cages have small holed wiring and something is killing them.
It ate ones head off and ate the head and leggs of of another I have set a live trap and other methods and still nothing. Any ideas
on what this is and how to get rid of it. Someone said it could be a weasel it would have to be skinny to get in the cages. Please
help.

 

[Mattemma]

I would set some leg and/or conibear traps along with live traps since some animals shy away from the live ones.Could get a game cam for $100 or less to see what is getting in.Could you move the birds to a more secure location for a short time? Basement or garage?
Conibears are cheap. I would get a few of those and set them up in the barn.