Sydney tragedy: Euthanasia campaigner Philip Nitschke denies contact with dad

Controversial euthanasia campaigner Dr Philip Nitschke has denied his group had contact with the Davidson father suspected to have gassed his family along with himself in an apparent murder-suicide.

Nitschke, dubbed "Dr Death", originally told The Australian newspaper that Fernando Manrique had downloaded his e-book The Peaceful Pill Handbook, which has a chapter devoted to the use of carbon monoxide in suicide.

Nitschke told The Australian that his group, Exit International, had "some contact" with the Manrique-Lutz family ahead of Monday's tragic discovery.

The bodies of Manrique, 44, Maria Lutz, 43, and their autistic children, Elisa, 11, and Martin, 10, were found in the family's Davidson home on Sydney's northern beaches, along with the lifeless body of the family dog.

Police have said they were investigating whether the family was gassed, with toxicology reports expected to show carbon monoxide poisoning in all family members.

Despite his earlier claims, Nitschke later clarified his comment, saying that after checking the database, Manrique had not downloaded the book.

"Fernando Manrique did not access our book," he told Fairfax.

Police have been unable to confirm whether Manrique, who was seen around and on the roof of the family home at the weekend apparently rigging up gas pipes, gassed the family with his wife's knowledge.

But the event has reignited discussion around euthanasia and assisted suicide.

Nitschke has been a leading voice in the fight for assisted suicide, advocating for it as a human right. But he did say the Davidson situation was tragic.

"Obviously this is a tragedy, although that sounds like I'm critical of them, which I'm not," he said.

"Obviously parents sometimes get taken to extreme levels of stress, and it's hard to be critical. It's easy for us to sit here and say we are critical ... but until you walk in their shoes, it's very hard to be critical."

Since the tragedy friends and family of the couple have revealed Manrique's wife struggled with the pressures of parenthood, caring for her two autistic children, and the isolation of living in the country.

In the days before her death, Lutz appeared happy and in good spirits, close friends revealed.

One friend, Peta Rostirola, told the ABC's 7.30 programme she was "excited" on Friday following a meeting where she was informed she would gain assistance from the National Disability Insurance Scheme (NDIS) for the two children.

"She'd had a meeting with the NDIS and she was so excited she was going to be getting all this help," Ms Rostirola recalled of her final meeting with her friend last Friday.

"She even felt guilty for taking that, she was just the most selfless person."

The couple's children were loved by teachers at St Lucy's Catholic School, where their struggles with intellectual disabilities were catered for.

The youngest child, 10-year-old Martin, has been remembered as a "prolific painter" and "gifted artist".

"That was how he communicated, through his art," deputy principal Susan Jones told The Daily Telegraph.

Martin's sister, 11-year-old Elisa, was also artistic, preferring a digital medium, the teacher said.

"Elisa would hold your hand in the sweetest way. She would look into your eyes and smile and lead staff around the oval," Jones said.

Though the family appeared outwardly happy, friends have revealed the couple had struggled with their relationship, particularly over care of the children.

A close friend told The City Paper in the couple's home country of Colombia that Ms Lutz had planned to leave her husband and return to the capital, Bogota.

Investigations continue into the deaths.

Where to get help

• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
If it is an emergency and you feel like you or someone else is at risk, call 111.