CHAGRIN FALLS, Ohio -- A 16-year-old boy was killed after he was overwhelmed by fumes trapped inside an aboveground fuel tank, authorities said.

Timothy Haas, of Auburn Township, was pronounced dead Friday at the Marathon service station where he was cleaning sludge from the gasoline tank with his father and brother, said Geauga County Sheriff Lt. John Hiscox.

Bruce Haas, 49, was working inside the tank when he was disoriented and overcome by fumes, prompting his sons to climb inside and help him get out safely, Hiscox said.

Soon after, both boys succumbed to the fumes. Geauga County Coroner Kevin Chartrand said initial autopsy results showed Haas most likely died from lack of oxygen. He also suffered chemical burns.

His brother, Paul, was transported to Cleveland MetroHealth Medical Center and treated for injuries. He is in stable condition, said Auburn Township Fire Chief John Phillips.

Bruce Haas, a private contractor, was hospitalized for injuries and released. He had been hired by Ullman Oil to clean the tank.

Firefighters pumped in oxygen and used harnesses to pull the brothers out of the tank, but the small, two-foot opening hampered rescue efforts, said Bainbridge Township Fire Chief Brian Phan.

Chartrand said officials are inspecting equipment used to force fresh air into the gas tanks to determine if it malfunctioned.

On Saturday, Timothy Haas' classmates took time to hold an emotional memorial.