Published by ProPublica, the footage casts doubt on agents’ care of Carlos Hernández Vásquez, who was found dead 20 May

Video of the US border patrol cell where a 16-year-old from Guatemala died of the flu shows the teen writhing and collapsing on the floor for hours before he was found dead.

The footage published on Thursday by ProPublica calls into question the border patrol’s treatment of Carlos Hernández Vásquez, who was found dead 20 May.

According to ProPublica, Carlos staggered to the toilet in his cell in the middle of the night at the border patrol station in Weslaco, Texas, and collapsed nearby. He remained still for more than four hours until his cellmate awakened at 6.05am and discovered him on the floor.

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The cellmate quickly got the attention of a border patrol agent, followed shortly by a physician’s assistant who attempted a single chest compression. Weslaco police reports obtained by ProPublica say the physician’s assistant quickly determined Carlos was dead.

The border patrol’s statement on the day of Carlos’s death says the teenager was “found unresponsive this morning during a welfare check”.

The video shows Carlos stopped moving at 1.39am on 20 May, 15 minutes after he toppled forward and landed face-first on the cell’s concrete floor. Border patrol logs say an agent performed a welfare check at 2.02am, 4.09am, and 5.05am.

Norma Jean Farley, the forensic pathologist who performed the autopsy, told ProPublica that she was told the agent looked through the window but didn’t go inside.

Police photos show a large pool of blood around Carlos’s head.

US Customs and Border Protection issued a statement on Thursday saying it could not discuss specifics of Carlos’s death due to an ongoing investigation, but that the agency and the Department of Homeland Security “are looking into all aspects of this case to ensure all procedures were followed”.

But CBP’s former acting commissioner, John Sanders, said he believed the US government “could have done more” to prevent the deaths of Carlos and at least five other children who died after being apprehended by border agents.

“I really think the American government failed these people. The government failed people like Carlos,” Sanders told ProPublica. “I was part of that system at a very high level, and Carlos’ death will follow me for the rest of my life.”

Sanders resigned as CBP was detaining thousands of people at a time, many for longer than the agency’s own 72-hour deadline, sometimes for weeks at a time. As border crossings surged this spring, Donald Trump’s administration sought to hold people for longer to end what it derided as the “catch and release” of immigrant families.

But the border patrol was not equipped to detain people for that long. Reports of people jam-packed into cells without drinkable water or showers sparked national outrage. One group of lawyers that visited a station in Clint, Texas, described seeing hungry children trying to care for each other and one four-year-old with matted hair who had gone without bathing for days.

The border patrol has since reduced the number of people in its custody – largely due to the rollout of policies such as “Remain in Mexico”, in which the US government has sent more than 55,000 people back across the border to await their court cases. Thousands of those people are now waiting in squalid border camps.