Okay, so I read the article online. I think we're forgetting that we all have a "mental disorder" (that's the wording in the article I read). I know I do, and I probably did when I was 16, too. I was fully competent to take care of 4 kids back then, still am, just would be a lot more worn out by it. So I don't think we can make any judgements there.
The article I read also said that things like this happen a lot more frequently than people realize. I just hope that everyone involved gets the help that they need - the parents, the babysitter, and the 5 year old as well. This is a horrible tragedy and all I can see is all the sorrow and pain that this family is going to be going through. Even if the 5 year old is found inculpable, that family is going to have to deal with mourning and stigma and judgements from everyone.