A family of four has been found dead inside a northern Sydney home, sparking a homicide investigation.
Officers made the grisly discovery at a property on Sir Thomas Mitchell Drive in Davidson on Monday morning when they responded to a call about concerns for the family's welfare.
The bodies of a 44-year-old man, a 43-year-old woman, an 11-year-old girl and a 10-year-old boy were found inside the home.
The children were students at St Lucy's School in Wahroonga and both were significantly disabled with autism.
The family's dog was also found dead in the home.
Police will not reveal the cause of the family's deaths, nor rule out whether investigators are searching for anyone in relation to the case.
"We are gradually working our way through this very tragic circumstance, to get to the bottom of it, to find out the truth about what has happened here today," Superintendent Dave Darcy said.
"There is no one at the moment telling us what has happened. There's no one who has witnessed this."
Supt Darcy said the tragic discovery was extremely confronting for his officers.
"We consistently have these sorts of concern for welfare cases and unfortunately in some cases, this is what the police are confronted with," he said.
"I think it's a horrific thing that's happened in this suburb."
Police are trying to contact the next of kin as the family are foreign nationals.
Supt Darcy said the family were well respected.
"The mother in particular is held in very high regard in the community," he said.
"Since coming to Australia they've made a significant contribution to how we live, they've done a fantastic job."
A neighbour, who has lived in the street for nearly 50 years, said the family moved to the area around 2005.
She spoke of seeing the children playing in parklands opposite their house.
The woman, who didn't want to be identified, said she had little to do with the parents and hadn't seen them in a while.
Another neighbour, who has lived nearby since 1979, said the quiet, leafy street had never experienced such a tragedy.
Forensic officers are examining the property, which is now a crime scene, while detectives speak to neighbours.
"This is an exceptional family. They've been at the school here for six years. Two beautiful children. And mum was a very active within the school - almost a cornerstone of the school in many ways," St Lucy's acting principal Warren Hopley told the media.
"I don't think she slept for many hours of the night because of the difficulties often with the two children, and yet she would always be here helping out in every way she possibly could."
Mr Hopley said he wasn't aware of any issues in the family.
He spoke to the mother most days and she was always positive, happy and greeted all 140 pupils at the school by name.
The school's teachers were all upset and in shock, he said.
"The children had very complex needs so you become very attached to them," Mr Hopley said.
"This was an enormous, enormous shock. It was terrible."
