Rattlesnake killed by feeder squirrel

[megaquake2012]

I was feeding my rattle a squirrel I caught and made sure was not sick with any disease or parasite I fed him to my rattle but to my surprise the squirrel charged at the rattlesnake and did a sort of crocodile death roll and kept biting at it before I could intervene my poor rattle got a big hole in his head which sadly got infected he later died why did this happen? I thought squirrels were commonly fed to snakes