A mother and her three children have been found dead at a home in Melbourne's northwest, with police investigating the possibility of a murder-suicide.
Officers were met in the backyard of the Tullamarine home on Thursday afternoon by paramedics and a 48-year-old man believed to be the husband and father of those found inside.
They were told to enter the Burgess Street property where they discovered the bodies of a 42-year-old woman, two girls - aged seven and five - and a three-year-old boy.
Their deaths are being treated as suspicious.
The man, who is understood to have made the call for help, is a person of interest and assisting police.
But acting Deputy Commissioner Robert Hill said officers cannot afford to make assumptions so early in the case.
"We should not draw any conclusions at this point of time at his culpability," he told reporters on Thursday.
"If one was to do so, that would be grossly unfair."
There is no history of family violence associated with the family and murder-suicide is one of several lines of inquiry.
"There are many questions yet to be answered," acting Assistant Commissioner Mark Galliott said.
The man was uninjured and is expected to be formally interviewed by homicide detectives on Thursday evening. Charges are not expected to be laid in the immediate future.
Mr Hill said police were not able to divulge the nature of the injuries suffered by the mother and her children.
No one else is being sought over the deaths and there is no risk to the community, he added.
Mr Hill noted it was the second event in a week involving the loss of children in horrific circumstances.
"The loss of life is tragic in any circumstances," he said.
"But when it involves children, it makes it even more heart-wrenching."
The deaths will have long-lasting effects on the extended family, neighbourhood, local community and first responders who attended the scene.
"It will impact the community of Victoria," Mr Hill said.
"Our police members on-site ... will be supported by our specialists within the welfare unit of Victoria Police.
"We will also provide support for the broader family members that have no doubt suffered significant emotional loss as a consequence of this event."
Neighbours of the family were left shaken to learn of their deaths.
"It's a shock because I used to live here before with my mum," one told reporters.
"I used to see the children, they used to play in the cubby house at the back. It's really sad."
Another said: "Horrible situation, right in your own backyard. It's just a door away from my mum's backyard."
Police, homicide detectives and forensic investigators are expected to remain on site long into Thursday night, methodically piecing together the circumstances of the tragedy.
"The broader community ... needs an answer to this," Mr Galliott said.
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Australian Associated Press