Hello noxlomos - I take your point that dogs are domesticated, but I still point out that domestication is not the same as removal of instinct. Domestication simply trains a dog to live in human society - it does not, and could not eradicate its urge to respond to its animal instincts, and this is the reason why these attacks happen.
I think you could expertly train a dog, and it could still turn, although the chances of it doing so are drastically reduced, the chance is still there, and as in these tragic cases, the animal only has to turn once.
I have to reiterate my point - dogs are unpredictable animals, training may reduce that unpredictability, but it will never eradicate it - and that is something that owners, and people with children who are around dogs, should always remember, and act accordingly. this was sadly not the case here, with tragic consequences.