Nik Rajkovic / news@whmi.com

The former safety director at the Oxford Center in Troy, where a 5-year-old boy died after a hyperbaric chamber he was receiving treatment in exploded, was sentenced Monday to 19 months to 15 years in prison as the judge said his "arrogance" led to the child's death.

Oakland County Circuit Court Judge Kwame Rowe told 66-year-old Jeffrey Mosteller that he was arrogant when he thought he knew better than experts and scientists who determined a grounding strap was necessary in a hyperbaric chamber.

"This is 'I think I know better than the national fire code,' 'I think I know better than the Seacrest manual,' 'I think I know better than my own training and experience,'" Rowe said.

The Oxford Center did not use grounding straps during treatment, something experts have testified prevented sparks in hyperbaric oxygen chambers and likely led to Thomas Cooper's death in January 2025.

Mosteller pleaded no contest to involuntary manslaughter in July. He was taken into custody at the end of Monday's hearing. An additional charge of second-degree murder was dismissed.

Three other defendants -- Oxford Center CEO Tamela Peterson; operations manager Gary Marken; and chamber operator Aleta Moffitt -- are still awaiting trial.

Peterson and Marken are charged with both involuntary manslaughter and second-degree murder. Moffitt is charged with involuntary manslaughter and entering a false medical record.

Thomas' family did not give a victim impact statement, as Assistant Attorney General Chris Kessel said they are not in a place where they can be in court to participate in the proceedings.

Judge Rowe said as the safety director, it was Mosteller's job to say something and insist that the grounding straps were needed.

"If these grounding straps were used, young Mr. Cooper would not have burned alive in a hyperbaric chamber," Rowe said. "I don’t think he intended to kill Mr. Cooper, but he created a situation where death was the likely and probable and foreseeable result. ... He certainly played a major role in creating this situation that caused Mr. Cooper’s death."

Prosecutors also alleged that Peterson, Mosteller and Marken ignored guidance from the chamber manufacturer's manual, the National Fire Protection Association and the Oxford Center's own training materials about safety in hyperbaric chambers.