Cannible Hamsters?

I had a few dwarf hamsters, maybe 11 or so., until a week a go. I noticed most of the hamsters gone, and I thought maybe some had escaped until I saw one dead, with its head and no body.. I also found 6 other dead hamsters... I had 4 left after I cleaned out the cage, and the other day I looked in the cage and I saw one of my younger hamsters eaten alive pretty much.. The other hamsters were hurled around it eating it.. They are being fed as usual, they are not low on food, I clean the cage, Ive been looking after them well. I thought it was Wet Tail, but I heard that was only with Syrian Hamsters. Whats happening?