Officers drag the boy to the ground, handcuff him, and force him into his cell.
Three guards restrain him face down while at least five others watch on. He's wearing nothing but a "rip-proof" gown.
An officer twists the boy's legs until they're crossed behind him and then sits on them.
"It's basically the hogtie," the boy explains.
"They push that far, you can feel your muscles burning and aching."
It's a practice known as "folding up".
The boy, Steve*, was in solitary confinement in juvenile detention, locked up in his cell for almost 24 hours a day.
*The names of all boys and their relatives in this story have been changed to comply with Western Australian laws around identifying children the subject of court proceedings.
Officers "folded up" Steve after he became agitated and kicked his leg through his open cell door.
"That day, I was stuck in the cell all day," Steve tells Four Corners.
"I never got a shower or nothing."
When an officer arrived with an evening meal, he tossed a piece of bread to the floor.
"They chucked that out on the ground like I was an animal. And personally, me, I wouldn't let that go," he says.
"I basically wanted to get out of the cell."
Six years after Four Corners exposed the brutal treatment of young detainees inside in the Northern Territory's notorious Don Dale facility, the program can reveal serious allegations of excessive force in Western Australia's only youth detention centre, Banksia Hill.
Officers at Banksia Hill are regularly using the folding-up or hogtie position, which has been banned in Queensland youth detention centres after a review found it posed a risk of suffocation and death.
For the first time, the public can see video footage from inside Banksia Hill of how children are being treated by authorities.
'I can't breathe'
Video of a second incident begins moments after Steve hit a guard with a mop at the door of his cell.
Body-worn camera footage shows five officers restraining Steve face down on his bed using the folding-up technique as he repeatedly begs them to ease the pressure.
"I can't breathe, I can't breathe motherf***ers," he cries out.
"Stop resisting!" an officer responds.
Steve describes feeling "helpless" during incidents like this.
"There's like a 100-something pound man on your legs, and they're trying to say, 'Relax and it won't hurt.'"
"How are you supposed to relax when you've got like four or five blokes on top of you?"
Four Corners has spoken to several boys who say they've been restrained like this at Banksia Hill.
One of them, Junior, describes it as getting "folded up like a pram".
"They would have your hands touch into your head and they'll put your legs there too. They're touching your back, your spine, and they'll just push until you're screaming," he says.
The Western Australian Department of Justice said in a statement that the restraint was "only authorised for officers to use as a last resort, in the most extreme circumstances, for as little time as possible, where there is a safety risk to staff and other detainees".
The department said approved restraint techniques "should not cause pain or injury".
Since 2017, Queensland has outlawed the practice in youth detention, after a report noted it was not used by any law enforcement agency in the country.
The Northern Territory royal commission into the Don Dale detention centre also examined the practice. It found the "application of force or bodyweight while an individual is handcuffed behind the back in a prone position" posed "significant risks of injury or death".
'Worse than anything you can imagine'
More than 600 children are locked up at Banksia Hill every year, many of them are Indigenous and many have severe neurological impairments.
The folding-up incidents happened while Steve was in the Intensive Support Unit, where children who misbehave or who try to harm themselves are sent.
Steve, who was recently released, has been in and out for several years for serious property offences.
He describes the conditions at Banksia Hill as "inhumane".
"It's been worse than anything you can imagine really … you can't go without laying on spit, blood et cetera. The cells are that filthy. You might as well stay at the tip," he says.
The WA government has consistently blamed a small cohort of detainees for the dysfunction in youth detention over the past 12 months, which has included violent behaviour, assaults on officers and severe staff shortages.
Its solution has been to confine Steve and other boys to their cells for nearly 24 hours a day, which has contributed to a drastic spike in self-harm incidents.
There have been more than 30 suicide attempts in youth detention so far this year.
"One boy ended up dying, and then they brought him back to life," Steve says.
He tried to harm himself on multiple occasions while isolated in his cell for long periods of time.
"Who wouldn't think like that because you're in that situation? It's depressing, stressful. You've got no-one to talk to. [You're] basically looking at four walls, and after a while it will slowly get to you."
Steve said there was a lack of support in youth detention for boys like him who were struggling with mental illness.
"Boys cry out for help but they don't do nothing. They're just screaming, crying, 'I want to kill myself.'"
"It's not really a place you want to be, but you've got no choice at the end of the day.
"You're in white people's hands."
'This is a young boy, not a man'
A week after the body-camera footage was recorded, family members visited Steve at Banksia Hill.
Jade says he had suffered multiple injuries from yet another incident.
"He had a black eye, he had grazing on the side of his face, his shoulder," she says.
After the family made a formal complaint about the injuries, the Department of Justice wrote to them confirming an investigation had taken place and "an outcome has been reached, the details of which are confidential".
"It makes you wonder what else are they doing in there to these kids," Jade says.
There are 10 staff currently under investigation over allegations of excessive force in youth detention in WA.
One officer has been charged with assaulting a child, over an incident earlier this year.
Another family member, Deborah, says she wants the footage of Steve released to expose the treatment of detainees.
"I want them to remember this is a young boy, not a man. A kid."
"These young boys are in pain, they're hurting, and they need to be believed that these things are happening to them."
'Barbaric': Boys sent to adult prison
The WA government took extreme action against Steve and 16 other boys in July after they smashed up cells and threatened to assault staff at Banksia Hill.
They were shackled and taken to a maximum-security adult prison where they were detained in a separate wing known as Unit 18.
WA Corrective Services Minister Bill Johnston defends the controversial decision, saying it's the only safe option while the government makes $25 million of upgrades to Banksia Hill.
"It's actually worked," he tells Four Corners.
"When we were able to get these violent young offenders away from the majority of the youth offenders. We've been able to get a much better environment for everybody, including the youth offenders themselves."
Child detainees kept at the adult prison continue to be confined to their cells for more than 20 hours a day on average. Lockdowns of this length were found to be "unlawful" in a Supreme Court case brought by the Aboriginal Legal Service earlier this year.
The president of the Children's Court, Hylton Quail, recently described conditions at Unit 18 as "barbaric", "cruel" and "a form of child abuse".
Judge Quail has warned the government its ongoing unlawful lockdowns of children are placing it at risk of contempt of court.
Aunty Pat has a young family member who has been detained in Unit 18.
While in detention he has assaulted guards.
Judge Quail described the teen's behaviour towards staff as "vile" but said he had suffered "33 days of essentially solitary confinement".
"When you want to make a monster, this is how you do it," Judge Quail said.
Aunty Pat says adult prison isn't a place for a child.
"It's not like a deterrent. It's like a concentration camp," she says.
"The children just get downtrodden, called all sorts of demonic and derogatory names. It just builds up a hatred and a real hardness in their life."
The WA government is facing a growing class action lawsuit over its treatment of children in youth detention.
Restorative justice advocates Gerry Georgatos and Megan Krakouer have helped gather testimony from more than 500 current and former detainees across the state.
"There's a sameness of these allegations by these children across hundreds and hundreds of testimonies … that they're physically abused, that they're locked down almost indefinitely," Mr Georgatos says.
"It's the unlawfulness but it's the human rights abuses, the rights of children being abused."
Don Dale continues to 'shock' commissioner
At the country's most notorious youth detention centre, Don Dale in the Northern Territory, allegations of serious abuse continue to emerge.
Four Corners' 2016 program, which exposed the use of spit hoods and the tear-gassing of boys in their cells, prompted a royal commission, which recommended the centre be closed immediately.
A new "world-class" youth justice facility focused on rehabilitation is still under construction.
"I am absolutely confident that we are not the system we were in 2016 when the youth justice system sat within adult corrections with adult prison officers," Minister for Territory Families Kate Worden says.
"We are not there anymore."
But the Office of the Children's Commissioner has received more than 400 complaints in the past year, involving problems such as solitary confinement and excessive use of force by guards.
"I've seen incidences which have, quite frankly, shocked me," Acting Children's Commissioner Nicole Hucks says.
Ms Hucks's office has released to Four Corners footage from an incident investigated last year, involving a boy who was at risk of self-harm.
CCTV shows three officers surrounding the boy's cell as they ask him to come out. After he calmly walks through the doorway, one officer grabs the boy by the neck.
He's wrestled to the ground by the staff members, who hold him face down for a minute and forty seconds.
The Children's Commissioner found the officers had used excessive force.
The Northern Territory government says it has already implemented 174 of the 218 recommendations from the royal commission.
But several of these – including the introduction of body-worn cameras – have been marked "complete" even after being rejected by the government.
Watch as Four Corners exposes the mistreatment of children inside Australia's youth detention centres tonight at 8:30 on ABC TV and ABC iview.
