Five people were killed and six were injured on Sunday when a car traveling east on the Long Island Expressway crossed a median, went airborne and struck two other cars, the Suffolk County police said. Among the dead was a former aide to Gov. Andrew M. Cuomo who had recently worked as an aide to the county executive, Steve Bellone.

The eastbound car, a Subaru, went into the westbound lanes around 9:35 a.m., landing near Exit 68 in Manorville, N.Y., the police said. The driver, Carmelo Pinales, 26, of Hicksville, and his sister Patricia Pinales, 27, of Westbury, were pronounced dead at the scene. Mr. Pinales’s son Christopher, 10, died on Sunday evening, the police said.

The Subaru hit a Honda, driven by the former Cuomo aide, Scott Martella, 29, of Northport, and a BMW. His passenger, Shelbi Thurau, 29, also of Northport, was treated for non-life-threatening injuries. They were engaged to be married.

In a statement on Sunday, the governor said Mr. Martella “was a dedicated, beloved public servant who worked day in and day out to improve the lives of his fellow New Yorkers.”