A Falls Church boy was fatally injured yesterday when a sport utility vehicle, left unattended with its gear in neutral, rolled down a steep incline and struck him while he sat with his mother at a bus stop at the Seven Corners shopping center, authorities said.

Tuan Phan, 4, was pronounced dead of head injuries at Fairfax Hospital a half-hour after he was hit.

The boy and his mother were at the bus stop on the west side of the shopping center's lower level in the 6200 block of Arlington Boulevard about 12:45 p.m. when the accident occurred.

A 1986 Toyota 4Runner parked about 200 feet from the bus stop rolled down the hill, gathering speed before it jumped the curb and hit the child with its front bumper, said Officer Onzy Elam, a Fairfax County police spokesman.

"The parking brake was apparently not engaged," Elam said.

It was not clear who had last driven the vehicle. Police identified its owner as Russell J. Lee Jr., 33, of the 19800 block of Billings Court in Gaithersburg. They said the investigation of the accident was continuing. Attempts to reach Lee by phone last night failed.

Neighbors in the Falls Church community said the boy's family, of the 2800 block of Mankin Walk, had moved in about a month ago.

One neighbor, Satima Goncalves, said her 3-year-old daughter often spent time with Tuan Phan, who would come to her house to visit.

"She loves to play with him and I don't know how to give her the news," Goncalves said.