Officers discovered 16-year-old Cleveland Dodd in the Unit 18 youth detention facility at Perth's Casuarina Prison on October 12, after he contacted them through the intercom.
He was taken to a Perth hospital in critical condition, where he later died, causing outrage and grief in the community.
About 300 people gathered in Perth's CBD on Wednesday to demand the unit be closed amid allegations the justice system had failed the teen.
The crowd chanted "Justice for Cleveland" and held placards accusing the WA government of having blood on its hands.
Cleveland's grandmother Glenda Mippy addressed the rally, saying her grandson's life had been stolen.
"My grandson never took his own life," she said.
"They call it justice but it's not justice ... Look what happened ... He got carried out on a stretcher.
"My grandson is lying in a morgue and why? Because they f**ked up."
Cleveland's other grandmother, Roslyn Sullivan, said her grandson was in the wrong place at the wrong time.
"He didn't get to be a man but hopefully his passing will make it better for the future," she said.
"I'm going to make it my business to know what they were doing to him."
Social justice advocate Megan Krakouer accused Premier Roger Cook of betraying Aboriginal people.
"Shame on this government," she said.
"To see the pain, the hurt, to see so many tears, is that right?
She said Cleveland had been unlawfully transferred to Unit 18.
"In terms of this young little fella, there are many questions that need to be asked.
"Why was Cleveland sent to Unit 18?"
Cleveland was the first child to die in WA juvenile detention in the state's history.
The area where he was found, Unit 18, opened in July 2022 to house the most challenging juvenile offenders after major riots at Banksia Hill Juvenile Detention Centre.
Both facilities have been plagued by high rates of self-harm incidents, riots and detainees being placed into prolonged lockdowns.
Cleveland's death is being investigated by the Department of Justice and the coroner while the Corruption and Crime Commission has also begun inquiries following allegations of serious misconduct.
The corrective services commissioner has also been replaced and a prison officer has also been suspended pending the outcome of the investigation into Cleveland's death.
Corrective Services Minister Paul Papalia announced the action on Wednesday.
He also said Corrective Services had been confronted by a series of critical incidents and crises over the past two years and juvenile detention was suffering.
"We need to reset, we need new leadership and we need a focus on cultural change (and) that's what we've done," he said.
Opposition spokesman Peter Collier said corrective services had been "weaponised" for political purposes to show off the government's "tough on crime rhetoric".
"In the meantime, the lives of inmates, in particular juveniles, are at risk and that's a shame," he said.
"What has gone, what has been lost in this whole ghastly episode is the fact that ... we are actually dealing with lives."
The Australian Greens said replacing the commissioner was a symbolic gesture and the Commonwealth should intervene in WA's justice system to "make sure that children are not being systematically abused".
The party also called on the WA government to close Unit 18 and said international human rights standards must be implemented.
"It is a national shame that a 16-year-old child with an intellectual disability has taken his own life in Unit 18, the first death of a child in custody in WA history," Senator Dorinda Cox said.
13YARN 13 92 76
Aboriginal Counselling Services 0410 539 905
Lifeline 13 11 14
beyondblue 1300 22 4636
18°C