It's so difficult to say ...... as far as an english bulldog being involved in this .. no I haven't heard any stories. Although, there is a story of an american bulldog attacking a toddler that was in the news recently.
I can't see how a dog would even think of a baby being a toy - a dog has animal instincts and would know that this was a living and breathing creature and not a piece of plastic.
Without knowing the dog in the past, I don't think anybody will ever truly know - it's just a terrible shame that it is a pitbull that has done this. Once more it's going to give every pitbull a bad name when I still believe that pitbulls are just the same as other dogs and it's the pitbull owners that are usually 99.9999% the ones who are to blame.