A 24-year-old father has appeared in Perth Magistrates Court charged with murdering his three daughters, aged under four, as well as his wife, before killing the children's grandmother the following day.
Anthony Robert Harvey allegedly killed three-and-a-half-year-old Charlotte Kate Harvey, two-year-old twins Alice Ester and Beatrix Mae Harvey, and their mother Mara Lee Harvey, 41, on Monday 3 September in their house in the northern Perth suburb of Bedford.
He is accused of murdering Ms Harvey's mother, the children's grandmother, 73-year-old Beverley Ann Quinn, in the same house the next day.
WA Police Commissioner Chris Dawson said police would allege a blunt instrument and knives were used in the crimes, but no firearms were involved.
He said the bodies of Ms Harvey and Ms Quinn were found in the kitchen of the house, with the children's bodies found in other rooms.
The five bodies were found yesterday after Mr Harvey went to a police station in the remote Pilbara town of Pannawonica.
Commissioner Dawson said police believed he had remained in the house on Coode Street for several days after the alleged murders, before travelling to Pannawonica.
Mr Harvey was charged this afternoon and appeared before Perth Magistrates Court via video link from Karratha.
'No words to explain the emptiness and loss'
Ms Harvey's sister Taryn released a family statement thanking everyone for their support during an "extremely dark and difficult time".
"There are no words to explain the emptiness and loss that we feeling," she said.
"Beverley was a kind-hearted, caring mother and grandmother and was always there for her family. She was very much family-orientated and she loved her daughters and grandchildren, and would have done anything for them.
"Mara loved being a mum and she loved her girls. She was so proud of each of them and was doing a great job of raising them. Her girls were her world.
"Charlotte was an energetic, bubbly, confident little girl who loved people and loved socialising. Alice was outgoing, adventurous and cheeky, while Beatrix was at times a little bit more quiet but gave the biggest hugs.
"This world is a sadder place with the loss of these five beautiful people but Heaven has gained five new angels."
Ms Harvey is believed to have worked in the Pilbara some years ago, and land title records show she bought the brick-and-tile home on Coode Street back in 2008.
Neighbours said an older woman visited regularly to help with the children.
Ms Harvey more recently ran a Jim's Mowing franchise with her husband, covering Morley and surrounding suburbs north of the Perth CBD.
Mr Harvey was described on their business website as previously working fly-in, fly-out in cleaning and grounds maintenance.
Latest in a string of WA mass killings
It is the third time this year that WA Police have been confronted by what appears to be a mass murder crime scene.
In May, seven people were found dead after a mass shooting in a house in Osmington, near the tourist town of Margaret River in WA's South West.
Katrina Miles and her four children were found shot dead in their beds, and the body of her mother Cynda Miles was found in an adjoining property with gunshot wounds.
The children's grandfather, Peter Miles, was also found dead from a gunshot and three firearms belonging to him were found on the property.
It was the worst mass shooting in Australia since the Port Arthur massacre in 1996, when 35 people were shot dead in Tasmania.
Then in July, a mother and two children were found dead in a house in Ellenbrook, in Perth's north.
The woman's son, Teancum Vernon Petersen-Crofts, alerted authorities to the crime after entering a nearby convenience store, where staff called police.
When officers went to the house, they found Michelle Petersen and her son, Rua, dead, and her daughter Bella in a critical condition.
She later died on the way to hospital.
Mr Petersen-Crofts has been charged with three counts of murder and remanded to the secure wing of Graylands Hospital while he awaits his next court appearance.