Mystery Dead Tawny Owl

I found a dead Tawny Owl on the canal towpath this evening near Park Nook Lock. The most perplexing thing about this is the fact that the owl appeared completely uninjured except for the fact that it was missing its face ! I have never seen anything like it, it head had been eaten/hollowed out completely from the face/beak inward to the back of the skull, yet the bird showed no other injuries at all. I cannot for the life of me work out how or by what it was killed ? I have stashed the remains on a wall (no bag to carry it with me at the time) and will try and get some photos of the injuries and post them on the blog. Does anyone have any idea about what happened here ?