The parents of a 10-year-old boy who was killed by a falling sign at an Alabama airport have filed a lawsuit against several companies responsible for designing, constructing and installing the sign, according to court documents.

The suit was filed by the Bresette family, who claim a sign at Birmingham-Shuttlesworth airport wasn’t secure and that contractors knew it posed a safety hazard. Nine contractors, designers and construction companies were named as defendants in the lawsuit.

A large electronic sign displaying arrivals and departures fell on the Bresnette family as they were waling through the airport in March.

Their son, 10-year-old Luke Bresette, was killed, and his mother, Heather Bresette, sustained several injuries, including two broken ankles, a broken pelvis, and a fractured tibia in the incident. Two of Luke’s siblings also suffered serious injuries due to the falling sign.

The family is seeking an unspecified amount in damages.