Maria Lutz and Fernando Manrique had a tenuous marriage that was in “serious trouble” before they were found dead in their Wahroonga home in October, an investigative piece by Ava Benny-Morrison for the Sydney Morning Herald claims.

Manrique’s long business trips and the difficulty of raising two young intellectually disabled children – Elisa, 11, and Martin, 10 – drove a wedge between the pair, close friends told the publication. Often, they said, the father would opt to travel overseas for the school holidays rather than spend time with his children, both of whom had autism.

“[Maria] would never have time to organise respite because it would be a last-minute thing – he would just go,” close friend and fellow mother at St Lucy’s, a special needs primary school, Peta Rostirola said.

"She kept saying, 'I have to untangle everything and it is taking me ages because I have to finish my study, deal with the kids and Fernando is away all the time.'"

'Untangling everything' reportedly involved Lutz, a trained criminal lawyer, consulting a solicitor in August 2015 about how to make the separation from her high school sweetheart as smooth as possible for her children - a meeting she never told Manrique about.

"She couldn't afford the emotional upheaval of presenting that to him because she needed to deal day-to-day with what she had," Nichole Brimble, friend and canteen co-worker, told the publication.

While the fractured marriage was well-known between the tight-knit group at St Lucy's, Manrique's possible mental health struggle was not - the only time Lutz alluded to it was a comment about her husband being "not in a good place".

One incident on August 17 this year, just two months before her family's tragic death, saw Lutz declare to friends she was getting a divorce.

Benny-Morrison writes that Lutz needed to take Martin to a specialist appointment that afternoon, yet despite calling her husband "three or four times" to ask him to pick up Elisa from school, Manrique refused. Martin quickly grew so ill he fainted and Lutz was forced to call triple-0. Lutz's last request from the back of an ambulance to pick up Elisa was denied by Manrique, who reportedly told her he was 'too busy in a meeting' to collect his daughter.

"Maria was done, that was the last straw," Rostirola said. "It wasn't anything about Maria wanting him there for her; she wanted him there for the kids and he just couldn't even do that."

Despite the rift between them, friends say Manrique was floored by Lutz's suggestion of a separation.

"He was completely shocked at the fact their marriage wasn't working," another friend Kerrie Dietz said.

Manrique is said to have told Lutz he would stay at home for the school holidays to help her with the children and organising the house before he moved out.

Lutz told her friends Manrique became highly engaged in family life, and was "continuously present" around the home.

Things were relatively peaceful until, during the second week of school holidays, Manrique took a loud 2am phone call, disrupting the sleeping children - who could be difficult to settle.

"Maria said she lost it," Brimble said. "She got so angry with him and told him he had to get out right then and there."

Reportedly, Manrique stayed at a hotel for two days before returning to the home under the condition he would use three weeks find somewhere to live. It was planned he would move to the Philippines, where he was heavily engaged in business, and would make regular trips to Australia to see the children.

Over these crucial weeks, during which Martin and Elisa returned to school and Lutz to her volunteering duties, police believe Manrique set about installing a complex poisonous gas system in the ceiling of the family home. Police sources also told Benny-Morrison that Manrique set up an account with a gas company, and obtained two large bottles of carbon monoxide in this time.

After authorities found the family of four, as well as their pet dog Tequila, unresponsive in their Sydney suburbs home, St Lucy's principal Warren Hopley was notified of the grim news, and given the harrowing task of telling Nichole Brimble.

The calls from Brimble are burnt into Rostirola's memory, she says.

"As soon as Nic rang and told me, I knew [Manrique] had done something," Rostirola claimed. "I think all of us knew straight away: he's killed them.

"Maria had this amazing group of friends and connections here, and she had a good life and he didn't."

Kerrie Dietz agreed.

"The final act of 'I don't actually need you any more', for a man who was very much in control of his world, his life, his business, must have led to his losing control."

Perhaps the most difficult task, the women say, is marrying Manrique's "quiet, hard-working" personality with what they believe he has done.

"This was three weeks at least of planning," Brimble said. "To think he was home all that time and planning it while playing with the kids and bringing them balloons and making them dinner … It just makes me sick."

Both Manrique's sister, Patricia, and Lutz's family, her parents Alicia and Ernesto and brother Alejandro, wanted a collective funeral for the family. Four coffins were set side by side in the Holy Name Catholic Church at Wahroonga.

You can read the full article by Ava Benny-Morrison here.

The investigation into the case of the Manrique-Lutz family is ongoing. 

If you or a loved one is suffering, Mamamia urges you to contact Lifeline on 13 11 14.