I don't know the circumstances about this latest tragedy; but I do know about dogs. Any dog is capable of biting; generally it is a last resort for a dog who has given every other signal that it is uncomfortable in a situation that it can. Unfortunately a big dog vs a person is going to cause more harm than a small dog. Even cats give nasty bites and scratches, although these are less life threatening to people.
Learn and look out for the signs. Behavourists call these appeasement signals and we also refer to the ladder of aggression. Dogs may have learnt that the signals are ignored, or (worse) punished by people. If your dog gets to the growl stage do not punish the dog, respect what it is saying and give it the space it is asking for. Your dog is not trying to be dominant or rule you, it is asking you to take notice of its feelings and to help it in a situation that it cannot remove it self from.
One report of the dog in Leicestershire says that the little girl was ill in bed and the mother was there tending to her child. For some dogs a crying child; and we don't know if this child was crying at the initial instance; can sound like a prey animal that is in trouble and their instincts kick in. Other things that can trigger a dog into a bite situation can be people hugging each other. Hugging is not something that dogs do or particularly like if it is done to them. Many dogs will try to split up a hug by getting in the middle of it. This triggers a reaction from people where the dog is pushed away, yelled at or even slapped, all of these can lead to a defensive bite from a dog.
The wonderful Lili Chan has great drawings on her website that illustrate dog body language beatifully http://doggiedrawings.net/post/842176625 please take the time to look at them.
For some good dog news. An abandoned baby was found by a dog. http://www.bbc.co.uk/news/uk-england-birmingham-24770596 and named after it.