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• Warning: this article contains distressing content

It was the kind of cold, damp morning that makes it hard to get out of bed, much less get a child out the door. The sun had not even risen when five-year-old Thomas Cooper and his mother, Annie Cooper, arrived for an appointment on 31 January at the Oxford Center in Troy, a northern suburb of Detroit, Michigan.

Thomas was an exuberant child with a button nose and pinchable cheeks – a little kid who loved running fast, playing Minecraft and watching Charlie and the Chocolate Factory, according to a GoFundMe set up by his family. He had just received money in a special red envelope for lunar new year, and he planned to spend it later that day with his little brother. But first, he was going to receive hyperbaric oxygen therapy for his attention deficit hyperactivity disorder and sleep apnea.