Anthony Robert Harvey, 24, is accused of killing his twin two-year-old girls, his three-year-old daughter, his partner and his mother-in-law.
Their bodies were found at the Coode St home on Sunday after Harvey visited a local police station.
The tragedy has stunned neighbours, who haven't seen the family in over a week.
"We thought they were on holiday, they haven't been there all week," Desrae Cambos told 7 News.
One neighbour told WA Today she often saw children playing in front of the house.
"It's just so sad, they've got primary school aged kids and I thought it just couldn't be," she says.
"It's sickening to think someone could do that."
Forensic investigators have been working into the night as they try to establish what led to their deaths.
Assistant Commissioner Metropolitan Region Paul Steel told local media on Sunday forensic and homicide police were conducting a "meticulous" investigation into the crime scene, which could take several days to complete.
The crime scene extends to a number of neighbouring streets, which have also been cordoned off.
The tragedy is the latest killing to send a ripple through Western Australia.
In May, Katrina Miles, her 13-year-old daughter Taye and sons Rylan, 12, Arye, 10, and Kadyn, eight, were all found dead at a private property in Osmington.
It's believed that the owner of the property, Peter Miles, is responsible for their deaths. Mr Miles and his wife Cynda were also found dead at the property.
In June, a 19-year-old male was charged with the murder of a 48-year-old mother, her eight-year-old son and 15-year-old daughter in Ellenbrook, a suburb in north-east Perth.