Inside the final weeks of tragic family found gassed in their home.

"Man, woman, two children found dead."

That was the heading on the brief media release from New South Wales Police on Monday that first told the country of the tragedy unfolding at Davidson, in Sydney's north.

Before any details were known it was clear something appalling had gone inside the well kept home, in a quiet neighbourhood unused to seeing local police, let alone the Homicide Squad.

That was shocking enough, but just as disturbing was the fact increasingly such tragedies are all-too common throughout Australia.

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Fernando Manrique and Maria Claudia Lutz - neighbours report he was working on the house two days before the family were killed. Photo / Facebook
Fernando Manrique and Maria Claudia Lutz - neighbours report he was working on the house two days before the family were killed. Photo / Facebook

What made the Davidson incident remarkable was the chilling lengths Fernando Manrique, 44, went to ensure not only his own life would end, but that of his wife Maria Claudia Lutz, 43, and their children 11-year-old Elisa, her brother Martin, 10.

'THEY DIED IN MY SISTER'S HUSBAND'S HOME'

The four deaths have now been referred to the NSW State Coroner. Police have said they are not seeking anyone in connection with the deaths and sources have told News Corp while detectives believe Mr Manrique gassed the family by himself, it cannot be completely ruled out Ms Lutz wasn't involved.

No note was found at the home. The family's computers are being examined to see if there is any evidence the mother knew what was happening.

Relatives who have paid tribute online about the dead family have made no mention of Mr Manrique.

Ms Lutz's sister, when asked what happened by a shocked friend, replied simply: "They died in my sister's husband's home."

WAS SHE PREPARING TO LEAVE?

In a sure sign Ms Lutz was struggling to cope under the pressure of having two autistic children, while her husband was often away, it is believed she was planning to quit Sydney and go home to Colombia.

The family's dog was found dead in the house, too. Photo / Facebook
The family's dog was found dead in the house, too. Photo / Facebook

The Daily Telegraph reported she announced her plans to leave a few weeks ago. It's believed her desire to leave was in contrast with her husband's plans. He had a successful, lucrative career and wanted to stay in Australia.

But Ms Lutz had told friends that enough was enough.

A close friend told The City Paper in Colombia the "marriage was struggling".

"With a marriage struggling over constant worries of the future of their severely autistic children, María Claudia wanted to return to Colombia."

It's thought they planned to visit Australia once a year. Anymore would be difficult with the children not being able to cope well.

"The children could not travel due to their health issues on a 14-hour flight and in order to comfort María Claudia, her family would visit Australia once-a-year."

The stress of bringing up the children was the heart of their problems, the friend said.

"She was going home this year, she decided."

GAS CHAMBER

One of the first questions asked by reporters at the hastily-called media conference at Davidson was "how did they die?"

Were there signs of violence? Any clues at all?

Superintendent Dave Darcy would not comment about the cause of death, deflecting question after question about what was found in the house. The only thing he would say was it was a "confronting" scene.

"It's an horrific thing that has happened in this suburb," Supt Darcy said.

The reality is police very rarely can provide much detail so early in an investigation. But in this case, chances are police were perplexed right from the start.

The family members, who were originally from Colombia, were not found together, but in separate rooms. Ms Lutz was found in the same room as Ella, Martin in another room alone, as was Mr Manrique.

They showed no visible injuries so it was impossible to know how they died.

What emerged was though was staggering. Police discovered a network of hidden pipes throughout the house that were used to transport the deadly gas that poisoned his family.

Gas canisters were also found in the home.

Neighbours saw Mr Manrique hard at work on the roof at the weekend, installing the system that would pump the gas - and end his family members' lives - into the rooms.

Maria Claudia Lutz Pena and children Martin and Elisa. Photo / AAP
Maria Claudia Lutz Pena and children Martin and Elisa. Photo / AAP

Neighbour Ofik Thomassian, 72, watched Mr Manrique working on the roof on Saturday.

"He was cutting and banging and making all sorts of noise and pulling up tiles but I don't really know what he was doing," Ms Thomassian said.

PRIVATE STRUGGLE: 'SHE FOUND IT IMPOSSIBLE TO COPE'

Both the children were autistic and their conditions heaped huge stress on the family, a close family friend told Colombian media.

They were both deaf and non-verbal.

The friend told the City Paper the family wanted to return to Colombia but had difficulty travelling far because of the condition.

In fact, Elisa escaped the family property earlier this year and was missing for five hours while the family searched frantically for her.

To combat the problem the family had to put up a fence to keep the children in. Ms Lutz later took to Facebook saying it was her "worst nightmare" her children would run away.

Ms Thomassian told The Daily Telegraph she spoke to Fernando regularly.

"He was very friendly and she was very protective of those children," she said.

So too was their mother.

"She (Ms Lutz) would lead them one at a time into the car, lock the door, and return to the house for the next child.

"She looked after them but I have to say she never looked happy.

"She always had a very serious look on her face. Thinking back now, she looked like she was in pain. She probably had been for a very long time."

Martin especially was a talented artist. The deputy principal at St Lucy's - where Ms Lutz often volunteered - where both children attended, said: "He was a prolific painter and a very gifted artist; that was how he communicated, through his art."

Ms Lutz was proud of it. She often posted his artwork for her friends on Facebook.

There were public hints to the private torment. Once, Ms Lutz asked via her social media accounts about Oreo biscuits. They were Martin's favourite - and she needed them to give him when he was well behaved.

Others who knew the family have spoken about how tired Ms Lutz was, as she would be awake often during the night with the children.

Neighbour Sonja Perry said Ms Lutz confided to her how hard it was.

"Maria used to tell me how hard it was on her and her husband. She said it was a heavy thing on her heart and some days she found it impossible to cope."

Where to get help:

Lifeline: 0800 543 354 (available 24/7)
Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
Youth services: (06) 3555 906 (Palmerston North and Levin)
• Youthline: 0800 376 633, or text 234 (available 24/7) or talk@youthline.co.nz or live chat (between 7pm and 11pm)
Kidsline: 0800 543 754 (available 24/7)
Whatsup: 0800 942 8787 (1pm to 11pm)
Depression helpline: 0800 111 757 (available 24/7)
Samaritans: 0800 726 666 (available 24/7)
If it is an emergency and you feel like you or someone else is at risk, call 111.