(CNN) -- — A 10-year-old boy was killed and several members of his family injured after an electronic information sign fell on top of them at an airport in Alabama.
Deputy Coroner Derrick Perryman said Luke Bresette was taken to hospital, where he was pronounced dead.
Two of his siblings were being treated for injuries while their mother, Heather Bresette, was in a critical condition at University Hospital.
Firefighters estimated the arrivals and departure sign at Birmingham Shuttlesworth International Airport weighed between 150 kg and 180kg.
Albert Osorio, 46, described hearing a loud boom when the sign fell, followed by the screams of the family and witnesses.
It took him and five other people to lift the sign off the family.
He said: "The whole thing flipped down on those kids. It took all of us here to stand it up."
Jefferson County Deputy Coroner Derrick Perryman said the family are from Overland Park, Kansas.
Airport spokeswoman Toni Herrera-Bast said officials were unsure how the sign fell over.
The airport continued to operate while rescue workers tended to the family.
It completed the first phase of a $201m modernisation effort and opened newly-renovated concourses last week.
Mayor William Bell issued a statement, saying the city offered its full support to the Airport Authority in investigating the accident.