WATCH: ‘I Can’t Breathe’: Video of Indigenous Australian’s Prison Death Stirs Outrage

SYDNEY, Australia — David Dungay Jr., a prisoner at a Sydney jail, told the guards pinning him to his bed that he couldn’t breathe, according to a video recording. He said it at least 12 times, in a high, panicky scream.

One guard’s response to Mr. Dungay was also recorded: “If you’re talking, you can breathe.”

Minutes later, Mr. Dungay, a 26-year-old Indigenous Australian whose family’s lawyer says he had schizophrenia, diabetes and asthma, was unresponsive. He was declared dead about an hour after officers first entered his cell.

On Monday, the graphic video footage was shown on the first day of Mr. Dungay’s inquest, reigniting long-simmering anger about the deaths of Indigenous Australians in custody, which are a flash point of race relations in Australia.

Indigenous Australians are one of the most incarcerated groups on earth. Aboriginal and Torres Strait Islander people are 27 percent of Australia’s prison population, despite making up about 3 percent of the country’s total population.

In 1991, a royal commission into Aboriginal deaths in custody made 339 recommendations, but many of them were never properly implemented, according to a report commissioned by Amnesty International Australia.

But the rate of incarcerated Indigenous prisoners since the commission has soared. Every single detained child in the Northern Territory is Aboriginal, according to data from June.

Mr. Dungay died on Dec. 29, 2015, in Long Bay Hospital, part of a prison complex in the eastern suburbs of Sydney, according to an opening address at the inquest by Jason Downing, the counsel assisting the coroner. He was serving a nine-year sentence for an attempted sex offense, assault and taking part in a robbery.

He became agitated after prison officers asked him to hand over a snack because of concerns about his blood-sugar levels, Mr. Downing said. A team of officers known as the Immediate Action Team then forcibly moved him from his cell, which did not have a camera, to one that did in order to monitor him.

In the video, which was shown at the inquest, Mr. Dungay is seen approaching the door before officers rush in, one with a riot shield, and pin him to the bed. Mr. Downing said the video was taken with a hand-held camera by one member of the team of officers.

“I can’t breathe, please!” Mr. Dungay is heard screaming. As officers escort him, hunched over, to the second cell, one is heard telling him to stop spitting blood in order to breathe.

They continue to restrain him in the second cell, when a nurse appears to administer a shot of midazolam, a sedative.

With a knee in his back, Mr. Dungay continues to cry out, insisting that he can’t breathe. Then he grows quiet.

Officers performed cardiopulmonary resuscitation on Mr. Dungay, and paramedics also tried to resuscitate him, Mr. Downing said.

He was declared dead about an hour after officers first entered his cell.

George Newhouse, principal lawyer of the National Justice Project, a rights advocacy group, is representing Mr. Dungay’s family at the inquest. He said that based on what had been presented at the proceeding so far, “When David lost consciousness, the response from the medical team was so inadequate that expert evidence suggested any chance that David might survive at that point was squandered.”

Mr. Dungay’s family was hoping for justice, he added, and that the coroner made recommendations to “ensure that this never happens again to another family.”

The “harrowing” video footage is a major reason this case has spurred so much outrage, said David Shoebridge, a state lawmaker for the Australian Greens who has been helping the Dungay family with the inquest.

“A young Aboriginal man with a very serious mental health condition is repeatedly brutalized,” he said. “No one should have to go through that.”

Last week, Western Australia’s police commissioner apologized to the state’s Indigenous people, acknowledging “wrongful past actions that have caused immeasurable suffering,” including Aboriginal deaths in custody.

In the United States, the words “I can’t breathe” became a rallying cry against police killings after the death of Eric Garner, an unarmed black man, on Staten Island, in 2014. In a widely circulated video, Mr. Garner told police officers that he couldn’t breathe 11 times, before he died.