Hundreds of Canberrans attending a vigil for Indigenous boy Cassius Turvey have been told growing old is a "privilege" for First Nations Australians.

The 15-year-old Noongar teenager was allegedly viciously bashed with a metal pole as he walked home from school with his friends last month, succumbing to his injuries 10 days later.

The death has sparked a national outcry, reviving conversations about the racism and disproportionate violence faced by First Nations Australians.

Several hundred Canberrans paid their respects during an emotional vigil at the Aboriginal Tent Embassy on Wednesday evening, part of 'a national day of action' to mourn the alleged murder.

Leah House, a Ngambri-Ngunnawal woman, told the crowd Aboriginal Australians are "not afforded the right to grow old" in their own country.

"For First Nations people in this country, it's a privilege to grow old. We should be ashamed by that," she said.

"We have lost so many young lives in this colony, [and] at the hands of this colony. We need our allies more than ever to stand up and show up."

Indigenous Australians are disproportionately the victims of deaths in custody, unsolved murders and disappearances, and a legal system which does not provide adequate justice to them, Ms House noted.

"What you are feeling tonight, leave and do something with that. I am sick of gathering on these steps mourning another life cut short," she said.

Mourners, who included ACT senator David Pocock, were greeted with a Welcome to Country, before taking part in a smoking ceremony and observing a minute silence.

Pausing at times to fight back tears, Ms House read out a statement from Cassius' mother Mechelle Turvey, delivered at vigils held across the country.

Ms Turvey said she was "overwhelmed and eternally grateful" to the thousands of Australians who had showed up in solidarity, calling for calm as people expressed their outrage.

"I am the only person who can get justice for my son, [so] stand beside me ... I am angry. Cassius' friends and family are angry," her statement said.

"[But] I don't want any form of violence at any of these rallies in the name of my child. Violence breeds violence."

Ms Turvey criticised police for failing to take a potentially "vital" statement from Cassius before his death, even while he was able to speak in hospital.

"The answer I want is: why?" the statement said.

"There was no contact with me, his mother. Why? It takes a loss of a loved one to get proper duty of care and an investigation. I feel that as a mum, I should have been kept in the loop."

Cassius underwent several surgeries in hospital after the alleged beating, but suffered a seizure and died more than a week after the incident.

A 21-year-old WA man is facing a host of charges - including murder - over the alleged attack, which also targeted Cassius' friends.

Police are yet to confirm a motive, but faced criticism for claiming Cassius had been "in the wrong place at the wrong time".

Earlier on Wednesday, Prime Minister Anthony Albanese described the death as a "murder", despite the matter not having gone before court.

"My heart goes out to the family and friends of Cassius Turvey. This is a human tragedy," he told reporters on Wednesday.

"A young man murdered in such an extraordinary, just terrible fashion. People are hurting and my heart goes out to them at this difficult time."