Four Michigan medical center workers have been charged in the death of a 5-year-old who was burned alive inside a pressurized oxygen tank that exploded.

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 was pronounced dead at the scene on Jan. 31 at the Oxford Center in Troy. His mother suffered burn wounds as she tried to save her boy.