His mother, Linda Frances Sidon, was anorexic, lived in a housing commission flat and, police would say, was an "anxious" and "fairly socially isolated person".
The New Zealand-born cleaner took medication for depression and was last seen at a doctor's appointment nine years ago.
This week, Heazlewood finally confessed to unlawfully killing his own mother and interfering with her corpse.
Now aged in his early 30s, Heazlewood has pleaded to manslaughter rather than the murder charge originally laid against him in October 2015.
Ms Sidon's body still lies somewhere in bushland in the Gold Coast hinterland.
It may never be found, despite Heazlewood assisting police with their search for her remains in thick scrub 30km southwest of the modest home she had shared with her son.
Police search the Numinbah Valley for the remains of Linda Sidon. Photo / News Corp
Her son, who frequented Gold Coast nightclubs such as Sin City, Shooters Howl and the Rendezvous Members Lounge, exhibited steroid-fuelled rage and wrote on Facebook about blowing up women with hand grenades.
And before his mother "mysteriously" vanished on June 19, 2009, the then 22-year-old boasted he had thrown her across a room "and was surprised at how far she went".
Police say the search was hampered by the length of time since her disappearance.
When he was charged with murder, Heazlewood's lawyer said the then 28-year-old was "quite taken aback when he was arrested" and "consistently denied having anything to do with her disappearance".
The case against Heazlewood, Mr Rosser said, was "largely circumstantial".
As well as sending an excavator and teams of officers with shovels to the Numinbah Valley, police used lasers capable of detecting blood under paint at her unit in the Gold Coast suburb of Ashmore.
For six years, Heazlewood had played dumb, pretending that his mother simply had never come home.
Police originally thought Ms Sidon, a recluse, might have taken her own life, perhaps overdosing on prescription drugs.
Linda Sidon was reported missing by her father almost 18 months after she was last seen. Photo / Supplied
Her disappearance went unreported for more than a year after the last sighting of her.
It was only her elderly father who raised the alarm with police in New Zealand in late 2010.
Ms Sidon's father told police he believed his daughter had been murdered because she had told him Heazlewood "beats her up a lot".
Gold Coast police began investigating and found that Heazlewood despised or was ashamed of his "bogan" mother.
In January 2011, Heazlewood told them that he "just came home one day and she was gone" and that he had "not made any inquiries to find her".
Police interviewed Heazlewood's friends, who allegedly said he disliked his mother and "spoke unkindly of her lifestyle, her appearance and her family".
Daniel Paul Heazlewood pleaded not guilty to the murder of his mother Linda Sidon. Photo / Supplied
A former girlfriend told investigators that Heazlewood was "mentally abusive and manipulative" and regularly used steroids in 2009 which made him "aggressive and violent".
Heazlewood had told her that he had "no respect" for his mother and that during an argument he had thrown her "across the room".
Police also read his Facebook page, finding a post written in 2012, three years after his mother disappeared.
It said "A lot of girls deserve a warm gift … such as a live grenade".
He also posted: "What do 80,000 battered wives have in common? They just don't know when to shut the f*** up."
In another post he swore off women saying "gym, xbox and porn is all this boy needs".
Mr Heazlewood was a member of the Gold Coast Pistol Club where he regularly used the firing range, and posted on Facebook about guns and his aim of being an army commando.
"Time to empty some clips," he said on a Facebook post in 2012. "1st ever shot with a 9mm Glock was centre bullseye … Die paper piggy."
Police search the home Linda Sidon shared with her violent son for clues to her death. Photo / News Corp Australia
One of Heazlewood's childhood friends, who had met his mother, told the Gold Coast Bulletin following his 2015 arrest that he was a "friendly and sweet person".
"He was always joking around and enjoyed a good laugh," she said.
"I can remember him always being there for me … I haven't seen him for a long time."
Another female friend told police that Heazlewood had threatened to "put your head through the concrete and put you in a place where no-one can find you".
Daniel Heazlewood, handcuffed at the Southport Watch House, after his murder charge which has been downgraded to manslaughter. Photo / News Corp Australia
In a statement to police, Ms Sidon's psychiatrist said the missing woman had previously told him that Heazlewood "was 'physically threatening' towards her".
In August 2015, Heazlewood allegedly told a female housemate that his mother was a "whore, bogan and a c***".
Police later traced trips by Heazlewood to the Numinbah Valley in 2009.
Daniel Haezlewood, who is in custody, will be sentenced on May 14.
