A 4-year-old boy and his father were critically injured when a gunman opened fire on a minivan Monday night in South Philadelphia, police said.

At 7:21, police were called to the 2700 block of Daly Terrace and found the boy and his 30-year-old father with bullet wounds, said Chief Inspector Scott Small.

The boy, who had been shot in the stomach, was taken to Children's Hospital of Philadelphia, where he was listed in critical but stable condition.

His father had been shot in the back and suffered a graze wound to the head, Small said. He was taken to the Hospital of the University of Pennsylvania, where he also was listed in critical but stable condition.

The father, his son, and a 9-year-old girl had just gotten into the Chevrolet Lumina minivan and were about to drive off when the gunman approached from the rear driver's side and fired at least nine shots, Small said. The back windshield was blown out, and exit holes were found in the front windshield.

"This van is riddled with bullets," Small said.

The girl was not hurt. "She's very, very lucky," Small said.

Her relationship to the father and son, who live in the neighborhood, was not immediately known.

The father, who was in the driver's seat when the gunfire erupted, is believed to be the target, Small said.

The gunman, described as a man in his 20s wearing a dark hooded sweatshirt, was last seen running west on Daly Terrace.