HOUSTON (AP) — A flu-ridden 16-year-old from Guatemala writhed in agony inside a U.S. Border Patrol cell and collapsed on the floor where he lay for several hours before he was found dead, according to video released Thursday that further calls into question the Trump administration’s treatment of immigrant families.

The footage published by ProPublica shows the last hours of Carlos Hernandez Vasquez, who was found dead May 20. He is one of at least six children to have died since December 2018 after being detained by border agents.

According to ProPublica, Hernandez 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 6:05 a.m. and discovered him on the floor.

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 Hernandez was dead.

Already, President Donald Trump has faced withering criticism for the thousands of family separations it conducted under a “zero tolerance” policy at the southern border and the squalid conditions under which it detained parents and children earlier this year.

U.S. Customs and Border Protection issued a statement Thursday saying it could not discuss specifics of the teen’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, told ProPublica he believed the U.S. government “could have done more” to prevent the deaths of Hernandez 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 said. “I was part of that system at a very high level, and Carlos’ death will follow me for the rest of my life.”

The Border Patrol’s statement on the day of Hernandez’s death says the teenager was “found unresponsive this morning during a welfare check.”

The video shows Hernandez stopped moving at about 1:39 a.m. on May 20, 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 2:02 a.m., 4:09 a.m., and 5:05 a.m.

Dr. 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 the teenager’s head.

Sanders resigned in June as the Border Patrol was detaining thousands of people at a time, many for longer than the agency’s own 72-hour deadline, sometimes for weeks on end. As border crossings surged this spring, President 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 Border Patrol station in Clint, Texas, described seeing hungry children trying to care for each other and one 4-year-old with matted hair who had gone without a shower 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 U.S. 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.