A 21-year-old man pleaded guilty to murdering the 17-year-old boy as he slept in his northern NSW home in the early hours of June 25, 2022.
The man had earlier received a text message from his younger sister suggesting the teen had raped her, a sentence hearing in the NSW Supreme Court was told on Monday.
None of those involved can be named for legal reasons.
In a fit of rage and under the influence of drugs and alcohol, the then 18-year-old travelled on foot several kilometres to his target's home, where he stabbed him multiple times until he believed he was dead, the court was told.
The teen's mother said she was woken by a dog barking and went into her son's room to check on him, only to be met with "an absolute bloodbath".
"I cannot unsee the horror of that scene," the distraught woman told the court.
"I can't unsee (my son) so completely drenched in his own blood that his dad and I were unable to find the wounds to stem the flow.
"The paramedics pulling him from his bed to the floor, trying again and again, and then eventually being told, 'he's gone'."
The killer addressed his victim's parents in court, sobbing and apologising for taking their son's life.
"I know that you two probably couldn't give less of a f*** what I have to say and that's OK," he said.
"I probably wouldn't either.
"I took your boy's life. It's my utmost regret, sincerest apologies, I'm sorry."
The man told the court he had grown up poor and at times homeless, and had been physically and mentally abused for as long as he could remember.
"This is not an excuse," he said.
"I own what I did with so much embarrassment and regret."
Crown prosecutor Brendan Campbell told the court the man had shown a determination for retribution and to take the law into his own hands, adding the claims of rape by the sister were entirely unproven.
"The agreed facts are very clear that it remains only an allegation," he said.
"It is not accepted that those events did occur as described by the sister."
Mr Campbell told the court the evidence suggested the victim had woken up during the attack and attempted to defend himself.
"Those last moments must have been filled with complete terror," he said.
The man said he would receive his sentence "with an open and accepting mind".
"I came here an 18-year-old kid and will leave a 30- or 40-year-old man and the whole world would have moved on without me," he said.
"And that's OK because I need to pay for what I did."
The case has been scheduled for sentencing on Tuesday.
5°C