I don't have a link to it but some time back there was a case where a chihuahua killed a baby. Now I don't know the details but it was on the news so a real case. I would think they must have left the dog alone with the baby.

You just don't leave a baby alone with any kind of animal. some people can sleep through earthquakes but if that's the case you know and before you doze off put everything right but still one of them should have been a normal light sleeper if they weren't druggies or just total idiots and just left the baby alone and came home to that.