Officers discovered 16-year-old Cleveland Dodd unresponsive in a cell at the Unit 18 facility at Perth's Casuarina Prison in the early hours of October 12, after he twice contacted them through the intercom and threatened to hurt himself.
He was taken to hospital in a critical condition, where he later died, causing outrage and grief in the community.
Cleveland Dodd's death in youth detention sparked outrage and grief in the community.
West Australian Corrective Services Minister Paul Papalia on Friday released the interim report of an internal investigation which he said had uncovered significant failures.
"Operational procedures were not followed on the night," he told reporters.
"Youth custodial officers were not carrying radios ... (and) record keeping was poor and not up to standard."
Mr Papalia said Cleveland was not placed under heightened-risk observation despite making self-harm threats, and staff checking inmates were not carrying radios.
The boy was also being held in a damaged cell and its closed-circuit camera was covered in toilet paper, obscuring its view.
"Two of the five staff required to wear body-worn cameras on the night did not sign out their devices," he said.
Mr Papalia said it was also found staff were watching movies in the control room at the time Cleveland self-harmed.
Another guard was partially undressed and "resting" in a darkened office nearby.
"None of these things are acceptable," he said.
"Collectively, they are disturbing and confirm the need for significant cultural change."
Corrective Servies Minister Paul Papalia said the report's findings were "disturbing".
The report also provided a detailed timeline of events before and after Cleveland self-harmed.
It started at 3pm the day before he died when the CCTV camera in his cell was covered with toilet paper.
At 1:22am, Cleveland called the control room where staff were watching a movie and made his first threat to self-harm.
Five minutes later, Cleveland made another call stating his intention to hurt himself.
The control room officer told Cleveland an officer would come to talk to him.
This happened less than a minute later and the pair spoke briefly before the guard moved on to speak to two other inmates.
At 1:40am, he returned to the teen's locked cell and found him unresponsive.
The officer then went to a supervisor's darkened office to retrieve Cleveland's cell keys and advise the senior officer about the incident.
The officer who found Cleveland was not carrying a radio.
At 1:42am, another youth detainee contacted the control room via the intercom and raised concerns for Cleveland's well-being.
Nine seconds later, the first responding officer opened a cell door and immediately started CPR on Cleveland.
A nurse and two other officers also responded and a code red was called throughout the prison at 1.53am.
Paramedics arrived 15 minutes later and found Cleveland still had a pulse.
Cleveland's death is also being investigated by the coroner and the Corruption and Crime Commission has started inquiries following allegations of serious misconduct.
The corrective services commissioner has been replaced and a prison officer has been suspended pending the outcome of the investigation into Cleveland's death.
Mr Papalia said Unit 18 would close as soon as a suitable replacement facility could be provided but declined to put a timeline on the closure.
Lifeline 13 11 14
Kids Helpline 1800 55 1800 (for people aged 5 to 25)
13YARN 13 92 76
Aboriginal Counselling Services 0410 539 905
11°C