The South Sudanese community lost a "beacon of hope" when a promising young basketballer was stabbed to death in an unprovoked street attack, his family says.
Alier Riak was out celebrating his 23rd birthday on March 13, 2022, when brothers Teamrat Kassa and Aron Gebregiorgis and four other men ambushed him and his friends.
They first went for Mr Riak's brother Kuol, punching and stabbing the 25-year-old on Bourke Street in Melbourne's city centre.
Mr Riak tried to defend his brother when the attackers turned on him instead, chasing him to a nearby park.
Kassa and Gebregiorgis repeatedly stabbed Mr Riak to the chest and leg before he was able to stagger back to his friends and then collapsed on the street.
CCTV footage shows Gebregiorgis calmly walking away from the scene and removing his bloodied jumper, while Kassa and the rest of his group remain near Mr Riak as police and then paramedics arrive.
Mr Riak died on the way to hospital, while his brother Kuol was taken to The Alfred with four stab wounds to his back and arms.
Gebregiorgis and Kassa were arrested and charged on March 18 over the violent attack.
They both pleaded guilty to murder in the Victorian Supreme Court on Thursday, while Kassa also admitted to recklessly causing injury to Kuol Riak.
Fourteen victim impact statements from Alier Riak's family and leaders of the South Sudanese community were read to the court.
They described how Mr Riak was a promising young basketballer who was due to start a new professional contract in Darwin in the days after his death.
He was also a mentor to WA's South Sudanese community, having lived there since he migrated with his family as a young child.
"Alier was a role model and a beacon of hope for his community," his mother Elizabeth Malek said in her statement.
"Our family once was happy but it has been shattered by this loss."
Kassa's only explanation for the murder was that "he heard something that he didn't like about something that had happened to an associate", his barrister Ashley Halphen told the court.
The 21-year-old had been released from prison on a community corrections order a week before the attack, he said.
He said the murder was not premeditated, and Kassa was a young man who acted impulsively while under the influence of Xanax and alcohol.
His brother Gebregiorgis was also abusing the prescription medication and cannabis before the murder, barrister Sam Norton said.
He submitted there was no explanation to justify his client's conduct but he had pleaded guilty and shown remorse.
Gebregiorgis handed himself into police before being charged and had since written a letter of apology to the court, Mr Norton said.
Kassa also submitted an apology letter but prosecutor Neill Hutton noted both statements were only written recently.
"It's somewhat convenient remorse - those letters weren't proffered 12 or 18 months ago," he told the court.
Mr Hutton said the murder was an entirely unprovoked attack on a group who were unarmed and trying to retreat.
Justice John Champion noted the gravity of the offending was elevated because Kassa and Gebregiorgis chased down their victims.
"A minute or so destroys everyone's lives for a lifetime," the judge said.
He will sentence the pair at a later date.
Outside court, Mr Riak's father James said the family was hoping for the best outcome from the judge.
"We are really very upset," he told reporters. "(Alier) was the icon of our family."
