TROY, Mich. (AP) — The safety manager at a suburban Detroit specialty clinic pleaded no contest to involuntary manslaughter Tuesday in the death of a 5-year-old boy who was inside an oxygen chamber that exploded.

The agreement with Jeffrey Mosteller calls for a minimum prison sentence of 19 months, Michigan Attorney General Dana Nessel said.

“A young child lost his life in a completely preventable tragedy because this defendant allowed an outdated device to operate in defiance of safety standards,” Nessel said.

The hyperbaric chamber at the Oxford Center in Troy exploded on Jan. 31, 2025, killing Thomas Cooper and injuring his mother who was standing nearby.

Mosteller’s attorney declined to comment about the no-contest plea. A second-degree murder charge was dropped as part of the deal in Oakland County court. Three more people, including the Oxford Center’s CEO, are awaiting trial.

After the explosion, the clinic said it couldn’t explain why it happened. A judge in February noted that safety concerns raised by employees “appeared to be all but ignored.”

Hyperbaric therapy delivers pure oxygen to a person’s body at about five times the amount of oxygen in a normal room. The FDA says it can be marketed as safe and effective for certain disorders, including severe burns, decompression sickness and wounds. The list doesn’t include many additional disorders advertised by the Oxford Center.