A 7-year-old boy was killed when he fell from a SEPTA subway car, authorities said Sunday night.

The accident happened shortly before 6 p.m., when the boy slipped between cars on the Broad Street Line near the North Philadelphia station at Lehigh Avenue, Philadelphia Police and transit authority officials said. He fell through to the tracks, and was struck by another car.

The 7-year old, his 11-year-old brother, and a 26-year-old man were selling candy to passengers on the moving southbound train when the boy fell between cars, said Sgt. Eric Gripp, a police spokesperson.

"We're not sure why or how he fell; that's all part of the investigation," said Heather Redfern, a SEPTA spokeswoman.

The boy, whose name was not released, was pronounced dead by medics who arrived shortly thereafter.

No other injuries were reported, Redfern said.

The Broad Street Line was shut down for a time between the Girard and Erie stations while the investigation was underway, and later resumed normal service.