The former safety manager of a medical center where a hyperbaric chamber exploded, killing a five-year-old boy, has pleaded no contest to involuntary manslaughter. Gary Mosteller, 64, faces a prison sentence of 19 months to 15 years.
Thomas Cooper, 5, died in January 2025 while undergoing Hyperbaric Oxygen Therapy at the Oxford Center in Troy, Michigan. The chamber burst into flames with the child inside. His mother attempted to save him but suffered severe burns.
Mosteller was one of four individuals arrested in March 2025 in connection with the boy's death. Prosecutors dropped a second-degree murder charge against him when he altered his plea to no contest on Tuesday. His sentencing hearing is scheduled for August 13.
Michigan Attorney General Dana Nessel stated that the tragedy was preventable and occurred because Mosteller allowed an outdated device to operate in defiance of safety standards. "While no outcome can reverse this loss, it is my hope that this conviction provides a sense of justice to Thomas’s family," Nessel said.
Hyperbaric chambers deliver pure oxygen in a pressurized environment, which can aid tissue healing and fight infections. However, a pure oxygen atmosphere is highly combustible if proper precautions are not taken. According to investigators, a static spark inside the chamber likely caused the fire that killed Thomas. This could have been prevented if the boy had been connected to a grounding strap, a piece of safety equipment found in a "junk drawer" at the facility.
Prosecutors argued that Mosteller ignored standard safety protocols outlined by the National Fire Protection Association and the chamber's manufacturer, Sechrist, which significantly contributed to the fatal incident. The Cooper family's attorney indicated that Thomas received multiple therapy sessions for sleep apnea and attention-deficit/hyperactivity disorder, conditions not approved by the U.S. Food and Drug Administration for such treatments. The attorney general described the treatments as medically unsound and the center as a "pure cash-flow, for-profit business."
Cases against the other three individuals arrested are ongoing. Tamela Peterson, 58, the Oxford Center's founder and chief executive, faces a second-degree murder charge. Facility manager Gary Marken, 65, is charged with second-degree murder and involuntary manslaughter. Chamber operator Aleta Moffitt, 60, faces charges of involuntary manslaughter and intentionally placing false medical information on a medical records chart. Peterson has also been accused of interfering with the investigation and reportedly made disparaging remarks about the boy's actions during the fire.
The Oxford Center stated after the explosion that the safety and wellbeing of its clients were its highest priority and that nothing similar had occurred in its 15 years of operation. The center said it would cooperate with investigations.