I read up on the research on familicide. The murder of your wife and child can be a response to financial or mental health issues. Many people suffer money problems and mental health issues but they don't just murder their wife and 7 year old.
But most commonly such cases involve rage, and is about control - it might be due to jealousy or emasculation, reflect issues about the male role, possessiveness and the need for control. Its key predictor is domestic violence or abuse.
Often after middle class cases people say that they seemed like a respectable family man, a good neighbour etc. But appearances are deceptive. Few of us really know what goes on behind closed doors in relationships. And wives and partners maintain respectable appearances too.
The fact that Emma called a family member on Saturday night may mean that her relative already knew about previous incidences or that they have an explanation from Emma herself about what was going on that night which may or may not become public.
But say her name and keep hold of the anger. Its not just their child who was an innocent victim.