Women DO sometimes kill their families.
I well remember a case when my DC were young, about the same age as the ones the mother killed (ages approx 5 and 3), by giving them a sleeping draft, and then smothering them while they slept. My parents sort of empathised with the mother whose husband had recently left. They implied that we don't know how people behave when something goes wrong, etc etc... I was so upset I had to rush upstairs to make sure my own DC were OK, and hear them sleeping softly, and I knew that I would / could never harm them in that way.
(I can't remember tho, whether the mother killed herself as well).
In this case, I supposed it must be murder suicide simply because it would be unusual for the police to be notified at 1.00 am, unless something had happened. I also supposed it was likely to be the father, simply because few women kill their DC in this way. (in my real life case above the DC were smothered).
I hope the true facts will emerge with the inquest. All I can say is that there were a lot of changes in the family. New home, new jobs for both, new school for daughter, and a dog, all of which may have caused some kind of stress that we know nothing about. Of course I am not justifying it. I really do not understand why people kill their entire family in this way.