18-month old twin girls, their 3-year-old sister, mother, grandmother found dead at a home in Australia

Police arrived at the north-eastern suburbs property about noon, where they found the bodies believed to include a mother, her three children and their grandmother. Unconfirmed reports state the children were 18-month-old twin girls and their three-year-old sister.

The Coode St address and surrounds have since been sealed off. Homicide detectives and forensic analysts have erected a pavilion on the street, at the intersection with Fort Street, as they initiate their investigations.

The man, said to be in his 20s, is said to ‘be known’ by the victims. He is in custody and undergoing questioning.

Police say there are no ongoing concerns for public safety as a result of this incident.

Neighbours said said a couple and their three children lived at the home but that they had not seen them in recent days.

Neighbour Desrae Cambos told journalists that the family, which seemed close-knit, had lived at the house for about four years with the father running a lawn-mowing and landscaping business.

Mrs Cambos said she had assumed the family had gone away on holiday because she had not seen the father’s ute parked in the driveway since last week.

A distraught neighbour said she often saw children playing in the front yard of the house at the center of police investigations.

“How could someone do that to their own children? It’s sickening to think someone could do that.”

Another neighbour told WA Today she didn’t know the home’s occupants personally, but would often wave and say hello as she walked past.

“It’s taken us by complete shock,” she said. “It’s just horrific on every level.”

Neighbour Vagner de Souza told the ABC he regularly saw a family in the house’s yard.

“Just a normal family, you would never imagine anything like that happening,” he said

The deaths came three months after a father shot dead his teenage son and daughter at their home in Sydney before turning the gun on himself.

It also follows the deaths of seven people, also in Western Australia, when a grandfather shot dead his wife, daughter and her four children in a mass murder-suicide in May.