What a horrific story
that poor LO and their family
I don't think the issue itself is the breed, any pet at all can just snap regardless of what they are. Think about yourselves, you can loose your temper without anyone actually teaching you/ telling you to do so right?
When I was in nursery, so like 2-3years old, a lady came to pick up her daughter and bought the family dog along, an Alsatian. The dog ran in all excited, ran up to that little girl, jumped at her, and bit her nose from her face...it was horrific and despite being so young, I remember it vividly.
Our own dog, Kelly a springer spaniel, jumped at me and spontaneously bit me in the arm when I was 5. Was enough for stitches.
The 2 dogs above weren't trained to do that, they just did it.
So IMO, all animals have the potential to just flip out, not just the 'dangerous' breeds same as we have the ability to just do a total 180 and change out temperament on the spot.
Hope this makes sense, it's 4:30am and I can't sleep so it may come across as ramble!