He wiped out most of his own family without any explanation.
Now one of Australia's most violent teen killers, Matthew De Gruchy, has sent a card to a family member, reminding them the countdown to his release has begun, news.com.au reported.
Years earlier, a checklist written by De Gruchy detailing his murder "plan" helped to convict the teen.
The 38-year-old is about to get a shot at freedom after 21 years behind bars for a suburban Sydney massacre so brutal it changed the lives of police who saw the murder scene.
De Gruchy faced a private parole hearing on Thursday, which could see him set free into the community he left in March 1996 when he bludgeoned to death his mother, sister and brother in their Illawarra home.
The attack was so sickening it scarred experienced police who are still haunted by the bloody mess the victims were left in.
De Gruchy was just 18 at the time of the murders.
News.com.au has learned he recently sent a note to a family member where he made a reference to his parole attempt.
The unsolicited note contained the usual greetings - he wished the relative and their loved ones well - but also made a pointed and surprising reference to the fact things were about to change for the family, which has tried to stay under the radar since the brutal murders made national headlines.
The note revealed his parole attempt was weighing on his mind and was something De Gruchy was looking forward to.
One family member, who spoke to news.com.au on condition of anonymity, said they could not understand how someone who killed three people could be released.
"They can't be rehabilitated, I don't think they can be ever changed after something like murder."
The source said killers like De Gruchy had "lost their soul" and questioned how he could fit back into the community easily.
"Surely he can't think he will just slip back in like nothing has ever happened?"
The biggest obstacle for everyone connected to the crime - all of whom were well aware of "the horror" that went on inside the De Gruchy home - was the lack of trust, which was impossible to win back.
"No I don't trust him, I wouldn't want to bump into him."
It was suggested at his criminal trial that De Gruchy flew into a rage when his mother wouldn't allow him to use the car.
"He may or may not get parole this time ... It will happen [at some point]. I don't wish him any harm because it doesn't change what happened. Other people talk about the death penalty, but it won't change what happened."
De Gruchy was jailed for a maximum of 28 years, but this is the first opportunity he has had to apply for parole.
While he was in maximum security prison at Goulburn he was charged over a fight with two brothers serving time for pack rapes.
The bashing almost killed one brother, who cannot be named. He suffered severe head injuries and needed brain surgery, while his brother was treated for a broken arm.
De Gruchy moved some time ago from Goulburn to a minimum security jail and is believed to have been out on day release already.
He has always denied the killings, insisting he was at the home of his girlfriend and found the bodies when he returned home.
His relative said "not a day goes by" they didn't think about the detectives and other police who investigated the killings.
Part of their healing process was not collecting too many things that reminded them of the tragedy.
"I don't know what can be gained for doing that. It's not harsh but at some point you have to move on, for your own sake."
It's understood submissions to the parole board included a desire for De Gruchy not to be released back into the Illawarra area.
"I don't want him there."
Some family members did keep in semi-regular contact with De Gruchy after his initial arrest. News.com.au is aware of one close family member who challenged him while he was being held on remand, telling him they didn't believe his story.
Matthew's father Wayne De Gruchy supported his son at trial and didn't believe he had committed the vile crimes. However, it is understood that in later years he approached senior detectives who worked on the case and asked again to see the evidence they had gathered to convict his son.
One of the most damning aspects of the Crown case was a checklist where De Gruchy detailed what he needed to do.
The note was found in a bag hidden in bush near De Gruchy girlfriend's home and included: "Sarah, Mum, Adrian", "Cut somewhere with knife", "hit arm with pole","throw bottle down the back", "have shower" and "hit head on bench".
Members of the police team who built the case against De Gruchy or saw the bloodshed in the home have spoken out previously about its impact.
One was so appalled by what they saw they never again worked in police, while former homicide detective Belinda Neil wrote in her book Under Siege last year of never getting over what she saw that day.
"The bed and pillow were covered in blood, so much blood that I knew her [Jennifer's] facial injuries would have been horrific," Ms Neil wrote.
"Whoever had killed this family had really gone berserk and inflicted incredible injuries. I still couldn't comprehend that a human being could do this to another human being."
De Gruchy went on a rampage through his family home in Albion Park Rail, an outer suburb of Wollongong, in 1996, bludgeoning to death his mum Jennifer, 41 and siblings Adrian, 15 and Sarah 13.
The murder weapon was never found but was thought to be a car jack or similar.
Mrs De Gruchy's body was found in her bedroom, Sarah's in her bed and Adrian outside in a shed. Their injuries were so severe that pathologists later said they looked like the victims of plane crashes.
Mrs De Gruchy's injuries were particularly devastating. Her brain had almost been forced from her head, and blood in her airways indicated she had been alive at least a short time after the assault.
Her face was so disfigured she was only able to be identified through a DNA match.
It was possible she and Sarah had been surprised while they had been sleeping. Sarah's arms were covered in defensive wounds suggesting she woke as the attack began and fought desperately for her life.
Adrian's lifeless body was found in the shed. He'd been covered in petrol, the can discarded a few metres away. The assault against him was so ferocious his blood was splattered on the ceiling. In total he suffered 21 separate wounds.
De Gruchy was the one who raised the alarm, running hysterically next door to a neighbour crying, "There's something wrong with mum and Sarah". He was later heard to say, "What has happened?" and "Who has done this?" as he was taken away to be assessed by ambulance officers.
Wayne De Gruchy was away in Sydney on business.
Matthew De Gruchy told police he had been at his girlfriend's place and came home on the morning of March 13, 1996 to find his family dead.
But homicide detectives didn't believe him. Three months after the triple murder that shocked Australia, the sole surviving De Gruchy child was charged with murder.