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 Jan. 31 at the Oxford Center in Troy. His mother suffered burn wounds while trying 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, adding many safeguards have been developed. 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.

— The Associated Press