Loved ones mourn slain basketballer stabbed to death in Melbourne

The South Sudanese community lost a "beacon of hope" when a promising young basketballer was stabbed to death by two men, 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 Riak's brother Kuol, punching and stabbing the 25-year-old on Bourke Street in Melbourne's city centre.

Riak tried to defend his brother when the attackers turned on him instead, chasing him to a nearby park.

Kassa and Gebregiorgis repeatedly stabbed 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, while Kassa and the rest of his group remain near Riak as police and then paramedics arrive.

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 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.

The plea hearing before Justice John Champion continues.