From piecing together bits from the above articles - in MOO I think the parents had been drinking leading to the late night meal, Scarlett had thrown the grapes at her father and he reacted badly and was threatening her with the knife, and probably misjudged how near he was. (100% not defending him). On the other hand he could be a horrible nasty bully that regularly gestured with knives if he wasn't hsppy. There are usually some truths sprinkled in amongst what is said. Again MOO
Alcohol might have been a factor in this tragedy.
I wonder if Police tested the parents with breathalyzer that fateful night.
JMO