I killed one of mine a couple days ago,it was real warm so i took them out in the yard,they are 4 weeks old,when i was putting them back in the brooder on the porch one started to run back outside I had a chick in each hand so I used my elbow to swing the door shut and the little feller was faster than I thought and he managed to get his head out but the door closed on his neck,broke his neck,he just started flopping on the floor I just stood there with my mouth open in disbelief,I was in shock that Id been so stupid,it wasnt like I couldnt catch him again I should have just let him run off the porch
I was told that sometimes things just happen,so dont beat yourself up too bad...if you have livestock sometimes you are just going to loose some
Take Care