Police found the remains of three young girls, as well as those of their mother and grandmother at an unassuming detached family home near the southwestern city of Perth on Sunday.

The gruesome discovery came after a 24-year-old man, who has not been named, walked into a police station in a remote mining area some 1,500km north of the city.

He was due to appear in court via video link later Monday.

The family has not been formally identified, but Australian media named the mother as Mara Quinn, a fly-in fly-out worker – an employee who is flown in temporarily to a remote location for a period of time – for a West Australian mining firm.

Her children were named as three and a half-year-old daughter Charlotte and two-year-old twins Alice and Beatrix, and her mother as Beverley Quinn, 74.

The police did not release details about when and how they were killed, or the family’s relationship with the man.

A Facebook profile believed to be Mara Quinn’s showed her cradling a newborn in her arms, with a man beside her, and stated that she was engaged in August 2014.

A real estate listing showed a modest three-bedroom house and a standalone garage.

“She was pretty unlucky in love before she met him,” a friend told Fairfax Media. “So (when they got together) it was like ‘yay, now she gets to start a family’.”