Too many people can't handle their dogs, many times when I used to take my spaniel out. He been attacked by 3+ terriers, rotties/ german shepheards amongst many others. Some times, you have to intervene whether for your own dog/or theres. (usually theirs-yes even the german shepherds )

p.s he chased a rabbit and got attacked by a horse

As for the OP, thats terrible. My brothers mate, had a rottie that savaged a kit. By all accounts, it was a pleasant dog, but some one had hit it with a stick. It lost its rag and went for the nearest thing.