3 charged with second-degree murder after 5-year-old killed in hyperbaric chamber explosion

Three people have been charged with second-degree murder after a 5-year-old boy was killed when a hyperbaric chamber exploded at a medical facility in Michigan earlier this year, officials announced Tuesday.

Thomas Cooper died on Jan. 31 in the incident at the Oxford Center in Troy, officials said.

The chamber contained 100% oxygen, making it extremely flammable, Lt. Keith Young of the Detroit Fire Department said at the time.

Safety protocols from the National Fire Protection Association and the manufacturer of the hyperbaric chamber were "completely disregarded" at the time of the boy's death, according to Michigan Attorney General Dana Nessel.

"Due to many failures by men and women who would call themselves medical professionals -- and wanton or willful disregard for the likelihood that their actions would cause the death of a patient -- 5-year-old Thomas Cooper was killed," Nessel said at a press briefing announcing the charges on Tuesday.

The owner of the Oxford Center, 58-year-old Tamela Peterson, and two other employees of the facility -- safety manager Jeffrey Mosteller, 64, and Gary Marken, 65, the primary management assistant -- have now been charged with second-degree murder in connection with his death, according to Nessel's office.

They also face an alternative charge of involuntary manslaughter. Nessel said a jury will ultimately decide if the state has enough evidence to prove the murder charge.

Nessel said they are confident the second-degree murder charge, which could potentially lead to a life sentence, is appropriate. The charge requires the prosecution to prove the defendant "knowingly created a very high risk of death or great bodily harm, knowing that death or harm would be the likely result of their actions."

Peterson's attorney, Thomas Cranmer, pushed back against the charges.

“What happened here is an unfortunate accident. This is not a murder case as the prosecution has alleged," Cranmer said in a statement. "We look forward to having all of the facts of this tragedy produced in a court of law."

Marken's attorney also maintained this was "an accident and not an intentional act" and denied the employee had any involvement in the hyperbaric chamber.

"We realize that everyone wants answers to how this happened, but that will have to be left up to the experts," the attorney, Raymond Cassar, said in a statement to ABC News. "The charges against him come as a shock to both him and his family as Gary was not involved with the overseeing of the hyperbaric chamber."

The operator of the hyperbaric chamber, 60-year-old Aleta Moffitt, also faces a charge of involuntary manslaughter and one count of falsifying medical records, Nessel's office said.

Moffitt's attorney described her as a "dedicated professional with many years of experience in the healthcare industry."

"She has always been a committed and hardworking individual, adhering to all corporate policies and procedures while prioritizing the well-being of her patients," Moffitt's attorney, Ellen Michaels, said in a statement. "As we move forward, we will carefully review all discovery materials provided by investigators and conduct a thorough analysis with the assistance of experts."

The Oxford Center said it has been cooperating with multiple investigations into the "tragic accident" and is "disappointed" in the decision to file charges.

"The timing of these charges is surprising, as the typical protocol after a fire-related accident has not yet been completed," the Oxford Center said in a statement. "There are still outstanding questions about how this occurred. Yet, the Attorney General's office proceeded to pursue charges without those answers."

"Our highest priority every day is the safety and wellbeing of the children and families we serve, which continues during this process," the statement added.

The defendants appeared in court in handcuffs for their arraignment Tuesday afternoon.

The prosecutor, Chris Kessel, argued that Peterson has been impeding the investigation, has the means to flee and was disregarding safety protocols. Meanwhile, Peterson's attorney, Gerald Gleeson, countered that she has not been charged with obstruction, is not a flight risk and that both her parents used the facility's hyperbaric chambers regularly, discounting that she was "operating these with reckless abandon."

A judge ultimately set Peterson's bond at $2 million and ordered that she not return to the Oxford Center's facilities and to cease all operations of their hyperbaric chambers, among other conditions.

"This is a very serious case," Magistrate Elizabeth Chiappelli said. "It involves the death of a young child in a horrific way. And I'm not going to use the term tragic because I think a lot of what we're looking at was disregard of safety protocols that created the risk of this happening. And that's exactly why we're here today."

Kessel alleged that Marken had been tampering with the hyperbaric chamber that exploded and had been rolling back the number of cycles to make it seem newer than it was.

"He was literally making this a ticking time bomb," Kessel said.

Cassar, Marken's attorney, said his client had not been to the Troy facility in over three years.

Chiappelli set both Marken's and Mosteller's bond at $250,000, while Moffitt's was set at $100,000.

The defendants stood mute, meaning a not guilty plea would be entered on their behalf.

Their arrests on Monday followed an "extensive and difficult investigation," Troy Police Department Chief of Police Josh Jones said in a statement.

Thomas was killed "within seconds" when a single spark appears to have ignited a fire inside the chamber, according to Nessel. His mother was also injured, authorities said.

"Fires inside a hyperbaric chamber are considered a terminal event. Every such fire is almost certainly fatal, and this is why many procedures and essential safety practices have been developed to keep a fire from ever occurring," Nessel said. "The investigation into this tragedy has revealed how the Oxford Center in Troy and several of its key decision makers held safety among their lowest considerations in their hyperbaric treatment practice."

Nessel detailed several safety standards she said were "completely disregarded by the Oxford Center staff" on the day of Thomas' death. According to Nessel, the investigation found that the daily maintenance check was not performed, the pre-dive safety check was not conducted on Thomas, an "essential" patient-worn grounding strap was not used, there was no medical doctor or safety supervisor on the premises at the time of the treatment and the treatment was not performed by a licensed technician.

Yearly inspections of the hyperbaric chamber, as suggested by the manufacturer, were also not conducted, according to Nessel.

"This was an unscrupulous business, operating powerful machines beyond their manufacturers' intended term of use on children's bodies -- over and over again -- to provide unaccredited and debunked so-called treatments, chiefly because it brought cash into the door," Nessel said.

The Oxford Center provides hyperbaric oxygen therapy for children with autism, ADHD and autoimmune diseases and other health conditions, the district attorney's office said. The Troy location has closed, while a second location in Brighton has ceased use of a hyperbaric chamber, Peterson's attorney, Gleeson, said during Tuesday's hearing.

An attorney representing Thomas' family said the arrests "mark a crucial step towards accountability."

"Under no circumstances should this have ever happened," the attorney, James Harrington of Fieger Law, said in a statement. "This tragedy highlights the need for stronger oversight, regulation, design safety features of hyperbaric oxygen therapy treatments to prevent similar incidents in the future."

"The Cooper family is committed to ensuring that those responsible for this unspeakable loss are held fully accountable," he continued. "It is critical that the justice system addresses the failures that allowed this to happen, and that steps are taken to protect our communities from these dangers in the future."