A massacre in a quiet Perth suburb has horrified residents who say the victims seemed like 'a normal, happy family'.

Two-year-old twin girls, their sister, aged three-and-a-half, mother and grandmother were found dead at a house in Coode Street, Bedford, on Sunday at 12pm (local time).

The ages of the children and their relationship to the two women were confirmed on Monday by WA Police.

A man aged in his 20s turned himself into a police station hundreds of kilometres away on Sunday before officers went to the house where they discovered the five females.

'The man currently assisting police remains in custody, no charges have been laid at this time,' police said on Monday.

It is unclear whether the man is related to the victims.

'It's just so sad, they've got young kids - it's horrific on every level,' neighbour Maria Manfredini told WA Today.

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Two-year-old twin girls, their sister, aged three-and-a-half, mother and grandmother have been found dead in a massacre at this property in Perth

Aerial footage has revealed a swing and children's toys in the backyard, including a plastic slide and toadstool-themed furniture

Coode Street resident Vagner D'Souza told ABC News the incident had taken the street by surprise.

'They just seemed like a normal family, you would never imagine anything like this happening here,' Mr D'Souza said.

Neighbours told reporters that they had not seen the family in at least seven days.

'We thought they were on holiday, they haven't been there all week,' Desrae Cambos told 7 News.

Police confirmed they did not know how long the bodies had been inside the Bedford house.

Ms Cambos revealed to Perth Now that the family's father ran a lawnmowing and landscaping business and she had not seen his work ute outside the premises for some days.

'It's just so sad, it's horrific on every level,' neighbour Maria Manfredini told WA Today

Streets in the area are still locked down but West Australia Assistant Commissioner of Police Paul Steel said there were no safety concerns for the public and no suspects are at large.

'Sadly at that location police have located the bodies of a number of deceased people including women and children,' he said.

'This is a tragic event and will have an impact on family and friends, the community, and the emergency services who first responded to the tragic scene.

'It will send a ripple through the community of Western Australia.'

'Police are conducting a thorough and proper investigation to determine what events led to this matter,' a police spokesman said

Detectives and homicide squad at the house in Coode Street in Bedford, in Perth's north east

The tragedy comes after a 19-year-old man was charged with murdering an eight-year-old boy, a 15-year-old girl and their mother at Ellenbrook in July.

At the time of the incident, Mr Steel said it was 'potentially the most horrific crime scene he has ever been called to'.

In July, four children and three adults were found dead at a Western Australia property in Osmington, in Australia's worst mass shooting since the 1996 Port Arthur massacre.

The bodies of Peter Miles, 61, his 58-year-old wife Cynda, their daughter Katrina, 35, and her four autistic children with estranged partner Aaron Cockman - Taye, 13, Rylan, 12, Arye, 10, and Kadyn Cockman, 8 - were found at the Miles residence.

Three firearms were located at the scene belonging to grandfather Peter Miles.