TROY, Mich. — Four people have been charged in the death of a 5-year-old boy who was “incinerated” inside a pressurized oxygen chamber that exploded at a suburban Detroit medical facility, Michigan’s attorney general said Tuesday.

Thomas Cooper from Royal Oak, Michigan, was pronounced dead at the scene on Jan. 31 at the Oxford Center in Troy. His mother suffered burn wounds as she tried to save her boy.

“A single spark it appears ignited into a fully involved fire that claimed Thomas’s life within seconds,” Attorney General Dana Nessel said.

“Fires inside a hyperbaric chamber are considered a terminal event. Every such fire is almost certainly fatal and this is why many procedures and essential safety practices have been developed to keep a fire from ever occurring,” she said.

The center’s founder and chief executive, Tamela Peterson, 58, is charged with second-degree murder. Facility manager Gary Marken, 65, and safety manager Gary Mosteller, 64, are charged with second-degree murder and involuntary manslaughter. The operator of the chamber when it exploded, Aleta Moffitt, 60, is charged with involuntary manslaughter and intentionally placing false medical information on a medical records chart. All were being arraigned Tuesday following arrests the day before, Nessel said.

NBC News reported that the family’s attorney said the boy received multiple sessions for sleep apnea and attention-deficit/hyperactivity disorder. These conditions aren’t among those approved by the U.S. Food and Drug Administration for marketing of hyperbaric oxygen therapy treatment — a fact reiterated by Nessel, who described the boy’s treatment as “unsupported by medical science.”

“Because these treatments were so medically unsound, patient insurance policies would not cover the use of these chambers to treat these conditions,” Nessel said. “This business was a pure cash-flow, for-profit business.”

The second-degree murder charge comes as “a total shock” said Raymond Cassar, Marken’s attorney.

“For fairness, he is presumed innocent,” Cassar said. “This was a tragic accident and our thoughts and our prayers go out to the family of this little boy. I want to remind everyone that this was an accident, not an intentional act. We’re going to have to leave this up to the experts to find out what was the cause.”

Moffitt’s lawyer, Ellen Michaels, also extended prayers and sympathy to Cooper’s family, while asking for “patience and fairness as this process unfolds.”

“This event has had a profound impact on so many, including my client, the community, and the first responders,” Michaels said in a statement to The AP. “I pray for healing for all those affected. Aleta Moffitt is a dedicated professional with many years of experience in the healthcare industry. She has always been a committed and hardworking individual, adhering to all corporate policies and procedures while prioritizing the well-being of her patients.”

The Associated Press also sought comments Tuesday from attorneys for Peterson, Mosteller, and the Oxford Center. The AP also left a message with the center, and emailed the family’s lawyers for comment.

The Oxford Center said shortly after the explosion that “the safety and wellbeing of the children we serve is our highest priority.”

“Nothing like this has happened in our more than 15 years of providing this type of therapy. We do not know why or how this happened and will participate in all of the investigations that now need to take place,” the center’s statement said.

Hyperbaric therapy, which delivers pure oxygen to a person’s body, about five times the amount of oxygen in a normal room, has been cleared by the FDA to be marketed as safe and effective for a list of 13 disorders including severe burns, decompression sickness and non-healing wounds. The list doesn’t include many of the other disorders advertised by the Oxford Center.

The FDA recommends only using hyperbaric centers inspected and accredited by the Undersea and Hyperbaric Medical Society. The Oxford Center doesn’t appear on the society’s February 2025 list of accredited facilities.

Nessel suggested that the boy’s death could have been avoided if safety measures had been followed. Instead, a maintenance check had not been performed that day, no medical doctor or safety supervisor was on-site and the treatment was not performed by a licensed technician. Yearly inspections had not been conducted, and “the essential patient-worn grounding strap was not used,” she said.

Experts consulted by investigators reached “horrifying” conclusions, Nessel said: “The Oxford Center routinely operated sensitive and lethally dangerous hyperbaric chambers beyond their expected service lifetime and in complete disregard of vital safety measures and practices considered essential by medical and technical professionals.”