A mother and her four children with autism were among seven victims of what authorities are investigating as a murder-suicide on the family’s rural farm in the Australia town of Osmington.

Police are focusing their investigation on the woman’s father as the potential gunman. The father was also found dead at the scene along with his wife, daughter and their four grandchildren, sources told The Weekend Australian.

“I can only describe [it] as a horrific incident,” Police Commissioner Chris Dawson said at a news conference, according to the Australian Broadcasting Corporation.

Dawson added, “Two firearms have been located.”

A family friend identified the victims to the network as Katrina Miles; her children Ryan, Taye, Ayre and Kadyn, ages 8 to 13; and Miles’ parents Peter and Cynda Miles, who owned and also lived on the property where Katrina home-schooled her kids.

Mark McGowan, the Premier of Western Australia, said in a tweet that the events were “tragic and shocking,” according to The Morning Bulletin.