15-year-old Cassius was known as a gentle giant. His killers have just been sentenced.

Content warning: Aboriginal and Torres Strait Islander readers are warned that the following story contains images of deceased persons. This story also deals with murder, which may be triggering for some readers.

On Thursday, October 13, 2022, Cassius Turvey was walking home from school with a group of friends in Perth.

A black Ford Ranger ute stopped beside them at about 4.30pm, and passengers emerged, allegedly shouting racial slurs and the word "run."

It is alleged that a 21-year-old amongst them caught up to Cassius and attacked him with a metal pole.

Rushed to hospital with serious head injuries, he was quickly transferred to the Perth Children's Hospital with two brain bleeds.

He was discharged after five days, but back in hospital within hours after suffering seizures and two strokes.

Cassius was placed in an induced coma, and died on Sunday, October 23. He was 15.

The 15-year-old's family has shared this photo of Cassius in hospital. Image: GoFundMe.

Jack Steven James Brearley, 24, and Brodie Lee Palmer, 30, were convicted in May of murdering the 15-year-old after a 12-week trial.

Mitchell Colin Forth, 27, who was also on trial in the West Australian Supreme Court for Cassius's murder, was found guilty of manslaughter.

Aleesha Louise Gilmore, 23, was acquitted by the jury of eight men and four women.

Sentences handed down.

On Friday, Brearley and Palmer were each sentenced to life imprisonment, with Brearley eligible for parole in October 2044 and Palmer in January 2041.

Mitchell Colin Forth, 27, who was also on trial in the West Australian Supreme Court for Cassius's murder and found guilty of manslaughter, was sentenced to 12 years, eligible for parole in January 2033.

Chief Justice Peter Quinlan said the killers had cut Cassius's life short in a horrendous and vengeful act of aggression, violence and brutality.

"Cassius Turvey was robbed of his life and of his promise ... all because you killed him, Mr Brearley," he said.

Brearley had a complete lack of remorse and had lied throughout the trial while giving evidence, falsely accusing Cassius of knifing him and attempting to blame an innocent man for the killing, Justice Quinlan said.

"Mr Brearley, you were the person who killed Cassius Turvey in that fit of rage and brutality," he said.

"While you did not intend to kill Cassius Turvey, your attack was persistent and sustained and only stopped by the arrival of Mr Palmer."

Justice Quinlan said Palmer had failed to accept responsibility for his crimes and there were few mitigating factors to reduce his sentence.

"You do not have the benefit of a plea of guilty ... and you do not have the benefit of good character," he said.

Justice Quinlan said Forth was never the main offender in the shameful course of events but always there in the background.

"You were just following along in the excitement of trying to be a tough guy," he said.

"And you followed Mr Brearley all the way to a conviction for manslaughter."

What we know about Cassius' case.

Brearley delivered the fatal blows on Cassius while "hunting for kids" because somebody had smashed his car windows.

He chased Cassius into bushland and knocked the teen to the ground and hit him in the head with a metal pole, causing bleeding in his brain that led to his death.

Palmer and Forth were at the scene and found to have a common purpose.

Brearley denied he struck Cassius with a pole, saying he only punched him after the teen knifed him and that Palmer did the deed, which he in turn denied as the two men attempted to blame each other for the murder during the trial.

Cassius Turvey.

The jury was told the attack on Cassius, in bushland, near a creek, was "the end point of a complex series of events that had absolutely nothing to do with him".

They started on October 9 when Forth, Brearley, Gilmore and another man, who was also on trial for lesser charges, Ethan Robert MacKenzie, 20, allegedly "snatched two kids off the street" and unlawfully detained them, punching, kicking and stabbing one of them.

The next incident happened three days later, on October 12, when a group of school-aged kids allegedly went to Gilmore's home and "almost certainly in retribution" smashed the windows of Brearley's car.

Mr Stanwix told the jury it was "tit-for-tat escalation" and Brearley and Forth had later used a car as a weapon and chased down two boys, hitting one of them.

The following day, Gilmore's brothers warned that a group of teens could be coming to their family home, where Brearley also lived, looking for a fight.

Brearley and his co-accused allegedly armed themselves with metal poles pulled from shopping trolleys before driving off to search for youths.

About the same time, Cassius and a group of about 20 fellow students caught a bus to the same area to watch a fight being talked about on social media.

Brearley, Forth and Palmer intercepted them near the field and, in a series of incidents, Brearley was allegedly slashed with a knife, and another boy was struck in the face with a metal pole.

Cassius and some other "terrified school kids" fled into nearby bushland.

"Cassius didn't make it as far as the fence when the accused Brearley caught up with him," Mr Stanwix said.

"He was caught, knocked to the ground and deliberately struck to the head with a metal pole."

Cassius was struck at least twice, the impact splitting his ear in half and causing bleeding in his brain.

His death shocked the community and the attack was described by some, including Prime Minister Anthony Albanese, as racially motivated, although Mr Stanwix said this wasn't the case in his opening remarks.

All told, the five defendants variously faced 21 charges over the events of October 9 and 13.

The jury found them guilty of all except Gilmore's murder charge, and a stealing charge faced by Brearley.

Cassius is being remembered as a gentle giant.

A year nine student and Noongar boy, who ran a lawn-mowing business in his spare time. As his mum told NITV, he didn't charge a set price for his services. Instead, he asked customers to pay him what they wanted to.

"He just wanted to let people know that the youth in our community, we’re not bad," Noongar-Yamatji woman Mechelle Turvey explained.

"He’s got a really strong sense of community, him and his mates."

The family only recently lost Cassius' father, Mechelle's husband, Sam, to cancer.

"I’m feeling heartbroken," Mechelle told NITV.

"I feel useless. Honestly, I feel so angry, like I want to do something and there's nothing I can do. I can't protect him from any of this.

"I've always told him, 'You're an Indigenous boy, they're going to look at you and think all these awful things, just try to be smaller.' I hate that I had to explain that to my son at this age."

You can find Cassius's family's GoFundMe here.

— with AAP.

This article was published on October 26, 2022 and has been updated since.