The family's pet dog was also found dead in the Davidson house. Photo / Facebook
Neighbours who saw him on the roof of the Davidson, north Sydney, home with power tools over the weekend had no idea he was rigging up what has been described as an elaborate system to pump gas into the rooms.
Detectives are investigating the source of the poison found in gas canisters as family members in their home city of Bogota, Colombia, revealed the couple, whose son and daughter were autistic, was on the verge of divorce.
The fiercely protective mother, Maria Claudia Lutz, 43, was found dead in one room with their daughter Elissa, 11. Their son Martin, 10, was found in another room alone.
Engineer and technology expert Manrique, 44, was found on his own in another room. The family's german shepherd was also dead.
BOC Gases employees help police remove two gas cylinders from the home. Photo / Craig Greenhill, News Corp Australia
Neighbour Ofik Thomassian, 72, who lives directly across the street, watched Manrique working on the roof on Saturday.
"He was right up on the roof replacing tiles and using power tools of sorts," Thomassian said.
"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."
The Davidson home where father Fernando rigged a deadly gas chamber for his family. Photo / Craig Greenhill, News Corp Australia
The bodies were discovered on Monday morning when staff at St Lucy's Catholic School alerted police after the children did not attend class and Lutz did not arrive to run the canteen.
Lutz was last seen on Friday after picking the children before having a coffee with other mothers.
BOC gas employees yesterday inspected the property, which was rigged throughout the roof to deliver the deadly fumes in what a police source described as an "extensive, elaborate and well planned" operation.
Police take away a laptop from the family home. Photo / Craig Greenhill, News Corp Australia
Police are leaning towards the fact that the Drake Business Logistics company executive acted alone but have not been able to rule out the possibility of a murder-suicide pact with his wife.
"We may never know whether she knew what was happening, we just don't know," a source said.
Police are also investigating "domestic tension" between the couple as relative's tributes on Facebook pointedly made no mention of Manrique.
A source close to Lutz, who wished to remain anonymous, has told the City Paper in Bogota that the relationship between the couple was "at times very tense due to the stress of bringing-up the children".
A woman places flowers outside the family murder crime scene in Davidson. Photo / Craig Greenhill, News Corp Australia
The source said Manrique had "become very distant" and that his wife felt "very alone" but they could not confirm that she was filing for divorce and custody of the children.
Computers were seized from the house to see if Manrique had been researching the gassing and for any hint Lutz knew about it.
Thomassian said he was friendly and she was very protective of the children.
"She would lead them one at a time into the car, lock the door, and return to the house for the next child," Thomassian said.
Flowers are being placed by locals outside the Davidson house where the family was found dead. Photo / John Grainger, News Corp Australia
"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."
Police have appealed for public help.
A heartfelt message to the family who died in the suspected murder-suicide. Photo / John Grainger, News Corp Australia
Loving mother a fighter to the end
By Danielle Gusmaroli
It was her fight that won Maria Lutz the most admiration; a selfless, dogged determination to give some level of normalcy to her two severely autistic children.
That much was abundantly clear yesterday as friends and relatives of the devoted 43-year-old mother honoured her with tributes and praise.
Maria Lutz fought to have a normal life for her children Elisa (left) and Martin (right). Photo / Facebook
As the Colombian Consulate makes arrangements to fly relatives to Sydney to identify the bodies of Fernando Manrique, his wife Maria and their two children, Maria's grief-stricken sister Ana Lutz took to Facebook to pen her despair, writing: "No one can say anything different than you being a warrior, always fighting for everyone!
"My cute doll. One more angel in heaven, an angel given to their children, life!!"
The deaths of the couple and their children Elisa, 11, and Martin, 10, have left family and friends reeling as reports emerged that the family was gassed.
Maria had endured difficult times raising two autistic children. Photo / Facebook
Maria had previously told of the sleepless nights and battles she endured raising two children who struggled with non-verbal autism, but frequently told friends they were "my life".
The couple, who left Bogota for Australia and have no immediate family in the country, arrived in Davidson in northern Sydney in 2005.
Close friend Peta Rostirola described Maria as "selfless" in the battles she fought raising autistic children: "You faced life head on with all the challenges it threw."
Maria campaigned tirelessly for children with autism and often volunteered at St Lucy's school's fundraisers.
St Lucy's principal Warren Hopley honoured the woman who "touched the lives of so many". "We are all struggling to come to grips with this profound tragedy," he wrote.
"Elisa, Martin and Maria have been such a source of inspiration for us all at St Lucy's over the years.
"I have been bombarded with expressions of support and love. Maria touched so many people's lives."
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.
