The prolific bank robber, who began stealing cars in his teens, became a mental health advocate after suffering a series of sexual abuses while in youth detention and prison.

His son and collaborator Ky Manser, 22, mourned his father's death on March 24, posting a picture of the pair.

"Words can't explain the pain this has put me through," he said.

Mr Manser spent 23 years in prison in NSW, Queensland and the Northern Territory and reported being brutally raped and injected with heroin from a young age.

This started a drug addiction Mr Manser struggled to overcome.

He spoke openly about the challenges facing victims of sexual abuse in prison and reported his experiences to the Royal Commission into Institutional Responses to Child Sexual Abuse.

"When I saw the head of the Catholic Church, George Pell, getting questioned about church cover-ups, it gave me a lot of faith that my story might be believed," Mr Manser told the ABC in 2022.

The ex-con said dozens of prisoners came to him with similiar experience of sexual abuse after he spoke out.

This encouraged Mr Manser to continue working with victims of institutional abuse, establishing an organisation called The Voice of a Survivor and amassing more than 130,000 followers on social media.

"Often victims carry a backpack of guilt, shame, anger and confusion. Going through the legal process allows them to hand that backpack back to the perpetrators and in turn, often live a more fulfilled life," Mr Manser said about his organisation, which was liquidated in 2023.

Mr Manser had formed friendships with a number of high profile Australians through his advocacy work and his podcast The Stick Up.

Australian rapper Ay Huncho, former NRL player Braith Anasta and Wizard Home Loans founder and businessman Mark Bouris were among those mourning Mr Manser on social media.

A number of fans also posted heartfelt tributes to the advocate.