A Sydney family of four, including two children with autism, was killed by a deadly gas believed to have been filtered through the ceiling in an elaborately-planned murder-suicide.
Fernando Manrique, 44, his wife Maria Lutz, 43, and their two children Elisa, 11, and Martin, 10, were killed in their Davidson home by "an airborne gas", which also claimed the life of their large dog, police said today.
Media reports suggest an elaborate system used to filter the gas into the home through the ceiling has been found as detectives probe the scene.
Neighbours have told of seeing Mr Manrique working on the roof of the house in the days leading up to the tragedy, the Daily Telegraph reports.
"There was a lot of pre-planning that went into this," an unnamed police source told the newspaper.
The four family members were found in three different rooms in the house.
Cause of death has not been determined but police believe the family died from an air-borne gas.
The bodies had no visible injuries and police are not searching for any suspects.
While the motive for the family’s death has not been officially determined, neighbours close to the parents believe the children’s severe learning disabilities put excessive strain on the household.
According to neighbours, Ms Lutz would spend many sleepless nights desperately trying to care for her children’s needs while ensuring they attended therapy appointments.
“Maria used to tell me how hard it was on her and her husband having two kids who were deaf and dumb,” neighbour Sonja Perry told the newspaper.
“She said it was a heavy thing on her heart and some days she found it impossible to cope. They were such a lovely, friendly couple.”
Just before noon yesterday, police were called to the family home on Sir Thomas Mitchell Drive in Davidson, following concern for the woman's welfare.
Superintendent Dave Darcy told media outside the home that the two officers who arrived first at the scene had found what they saw "extremely confronting".
"An horrific thing that has happened in this suburb," he said.
Ms Lutz, who is a volunteer worker at a local school canteen, was "held in very high regard", Superintendent Darcy said.
"Since coming to Australia [the family have] made a significant contribution,” he said.
It is believed police were called after the woman had failed to show up at work yesterday morning.
A neighbour, who has lived in the street for nearly 50 years, said the family moved to the area around 2005 from Colombia.
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.
The children were enrolled at St Lucy's School in Wahroonga, a Catholic school that caters for children with intellectual disabilities.
"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 reporters.
"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."