BIRMINGHAM (AP) — A sign at the Birmingham airport fell on a family Friday, killing a 10-year boy and injuring other family members.

Deputy Coroner Derrick Perryman said 10-year-old Luke Bresette was pronounced dead at Children's of Alabama. Two other children were being treated there, and the mother, Heather Bresette, was taken to University Hospital, where spokeswoman Nicole Wyatt said she was in critical condition. The coroner's office and the hospital did not disclose the family's hometown.

Firefighters estimated the arrival-departure sign weighed 300 to 400 pounds.

Albert Osorio, 46, of Birmingham told al.com that he was close by when the sign fell. He said a loud boom was followed by screams from the family and witnesses. Then he and five other passers-by lifted off the sign.

"The whole thing flipped down on those kids. It took all of us here to stand it up," he said.

Airport spokeswoman Toni Herrera-Bast said officials aren't sure how the sign fell. She said it happened about 1:30 p.m. Friday in a pre-security area of the airport. The airport continued operating while rescue workers tended to the family.

The airport completed the first phase of a more than $201 million modernization 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.