A mother and her three children found dead at a property in Melbourne's northwest have been identified.
The bodies of 42-year-old Katie Perinovic, her two girls Claire, 7, Anna, 5, and three-year-old son Matthew were found inside the home on Thursday afternoon.
Her husband, Tomislav Perinovic, 48, was also at the Tullamarine site on Burgess Street, police said.
"We understand the three children were siblings. We also understand the three children were that of the female that was found deceased," Acting Deputy Commissioner Robert Hill told reporters.
"We also understand the male was the husband of the deceased female, and the father of the three children."
Mr Perinovic is assisting detectives from the Homicide Squad with their inquiries and the next of kin have been notified.
"At this point in time, the investigation is in its very early stages," Hill said.
"Investigators do not believe there are other parties involved at this stage.
"It's very important we do not speculate. The circumstance of this event are yet to be determined.
"We cannot afford to make any assumptions as to what occurred."
Hill said police would work through the crime scene methodically and the man had provided police with his account of what happened.
"It is a tragic event to lose life, in any circumstances," he said.
"But when it involves three children — the second event this week where we've seen the loss of children in horrific circumstances — it does impact upon the community."
Acting Assistant Commissioner Mark Galliott said police would remain at the scene all night.
"The loss of young lives in circumstances such as this is are difficult to comprehend," he said.
"This will have long-lasting effects on the police that have attended, on extended family, the community, the neighbourhood, the emergency services, and everybody else involved.
"They'll be lifelong memories that they'll have to deal with."
Galliott said information indicated the man was not injured.
"I understand that it was the male person at the address who contacted emergency services," he said.
There was no family violence history associated with this family, Hill said.
Asked if it could be a murder-suicide, he said there were "a number of possibilities and that's one".
Police would not reveal details about any injuries the victims suffered.
A neighbour told NCA Newswire it was "awful".
"There's people everywhere, police everywhere," she said.
She said she heard sirens about 12.30am but did not hear anything unusual beforehand.
"My son actually came and said you've got to have a look at this Mum, when the commotion started," she said.
Another woman who lives in the same street also said she did not hear anything before the police arrived.
"We were wondering what the hell is going on?" she said.
"We've never seen this many cops in this area.
"It's so sad."
The woman said it was a nice neighbourhood where children felt safe playing in the street.
She did not know the children who lived in the house, but said she believed they went to the local primary school.
"You don't expect that many police in this area — this is a quiet area," she said.
Anyone with information is urged to contact Crime Stoppers.
- NCA NewsWire