Troy hyperbaric chamber explosion: Man pleads no contest in fire that killed 5-year-old
Ex-safety manager pleads no contest in fatal hyperbaric chamber explosion
Jeffrey Mosteller pleaded no contest to involuntary manslaughter in the explosion that killed 5-year-old Thomas Cooper.
FOX 2 - The ex-safety officer at the site of a hyperbaric chamber explosion that killed a little boy, pleaded guilty to involuntary manslaughter Tuesday.
The backstory:
In exchange for the plea, Gary Mosteller had his charge of second-degree murder dropped by the prosecutor's office.
Per his plea and sentencing agreement, he will be sentenced to 19 months to 15 years’ incarceration, announced Michigan Attorney General Dana Nessel's office. Mosteller is scheduled to be sentenced on August 13.
The explosion killed 5-year-old Thomas Cooper and badly injured his mother at the Oxford Center in Troy on Jan. 31, 2025.
Still facing charges are Oxford CEO Tamela Peterson and management assistant Gary Marken for second-degree murder as well as employee Aleta Moffitt.
"A young child lost his life in a completely preventable tragedy because this defendant allowed an outdated device to operate in defiance of safety standards," Nessel said in a statement. "While no outcome can reverse this loss, it is my hope that this conviction provides a sense of justice to Thomas’s family."
The Oxford Center provided therapy for adults and children with health conditions like autism, ADHD, and autoimmune diseases, through Hyperbaric Oxygen Therapy.
Thomas Cooper, 5, was killed in a Jan. 31 explosion in Troy.
The hyperbaric chamber fire:
The hyperbaric chamber caught fire from the inside and exploded.
Both the National Fire Protection Association (NFPA) and Sechrist, the manufacturer of the hyperbaric chamber, publish strict safety protocols that Mosteller ignored at the time of Cooper’s death.
In a prior hearing, the prosecution revealed a grounding strap used for the chamber was found in a "junk drawer" at the center.
A grounding strap would have grounded Cooper and likely would have prevented the static spark that caused the explosion, an expert testified in a December, 2025 hearing.
Inset: Victim Thomas Cooper. Main photo: The remains of the Oxford Center's hyperbaric chamber.
Ex-employee's warnings ignored:
A former employee of the Oxford Center told FOX 2 in fall of 2025 that her safety pleas fell on deaf ears.
Tiffany Hosey worked there for about four years as a hyperbaric technician and said she had warned Peterson, and Mosteller, that patients were not being strapped with grounding bracelets.
Those straps she says, help prevent dangerous static sparks inside the chambers.
More coverage:
Oxford Center employees bound for trial in boy's death
Witness: Safety item not used in hyperbaric chamber fire which killed boy at Oxford Center
New details revealed in Troy hyperbaric chamber explosion case that killed 5-year-old
Tamela Peterson allegations:
In addition to lacking property safety measures, Peterson is accused of interfering with the investigation and criticizing Cooper while he was on fire.
Sources say Peterson allegedly shared CCTV photos of the boy and made disturbing comments about him.
"If my leg was on fire, I would at least try to hit it and put it out. He just laid there and did nothing," Peterson allegedly said.
Magistrate Elizabeth Chiappelli made reference to the claim of Peterson sharing photos from inside the center when Peterson was arraigned.
Tamela Peterson
AG Nessel rips negligence:
The state attorney general has not held back on the Troy Oxford Center tragedy which should have been avoided, she said.
Nessel said "horrifying and simple conclusions were reached" after the state's investigation spoke to experts on hyperbaric chamber treatments.
She added said the center routinely operated sensitive and lethal, 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.
Nessel said the Oxford Center routinely operated sensitive and lethal, 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.
Tamela Peterson, left, Gary Marken, Jeffrey Mosteller and Aleta Moffitt.
The Source: Information for this report is from previous coverage and the Oakland County Prosecutor's Office.