Details starting to emerge now.

Daughter with four autistic children breaks up with husband and the five of them move into a converted shed on her parents' 30-acre hobby farm. Her father shoots his daughter, grandchildren, wife and himself dead.

Awful.

http://www.abc.net.au/news/2018-05-13/margaret-river-murder-suicide-mystery-of-miles-family/9755116

The father of the children says he has been cut off from his kids by the grandparents for six months, there was a custody battle, and the grandfather had thought this through.

https://www.smh.com.au/national/nsw/peter-didn-t-snap-he-thought-this-through-father-of-shooting-victims-speaks-20180513-p4zezt.html

According to the kids' father, the grandfather had lost a son to suicide and now a second son was seriously ill with kidney problems and most likely the grandfather couldn't cope with losing him as well. But he couldn't top himself because the grandkids and he were too close and he couldn't leave them without him. So the twisted solution was to take out everyone.

http://www.abc.net.au/news/2018-05-14/margaret-river-murder-suicide-peter-miles-pain-behind-killings/9756918