10/13 chicks killed, what could it be?

[KWAK]

The chicks were about 3-4 weeks old in an outside brooder, forgott to close the lid this morning before school and came home to find 3 chicks outside the brooder hidding in the corner of the shed, looked in to find 1 body with out a head, and 9 pairs of wings...

Only the wings of 9 birds?
what ever it was didnt touch my pigeons (thankfully) who,s wings are clippped.
This is the 2nd time of this happening

and now I am really bummed out

because these were my 1st olive eggers from my flock... well at least i have the three

Any idea's of what it couldd have been?
Btw I live in MI...

 

[Ole rooster]

Not to be mean but it sounds like forgetfulness kill um to me. That and a dog.

 

[mrpekinduck]

Yeah that sounds like a dog or raccoon ( they do often come out during the day)

 

[sourland]

Time to lock the pens, set traps, and eliminate the problem before all of your birds are eaten.