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.

Michigan Attorney General Dana Nessel has charged four people in connection with the death of a 5-year-old boy who was killed in a hyperbaric chamber explosion.