Two children were killed as they walked to their school bus Thursday morning in Buckingham County, Va.

WTVR-TV reports a tractor-trailer hit the children as they crossed Route 15 in Dillwyn. A man at the scene who said he was the grandfather of one of the victims said the children were 5 and 6-year-old cousins.

The mother of the 5-year-old girl identified her as Tori Perez.

The crash occurred on Route 15 near Baptist Union Road at about 7:40 a.m.

The school bus was in the southbound lane, with yellow flashing lights on, as it had not come to a complete stop, Virginia State Police spokeswoman Corinne Geller said. Red flashing lights and stop sign are triggered when the vehicle comes to a complete stop.

As the bus approached, the two young children began to run across the road, and four other students stayed behind.

The school bus driver saw the oncoming truck and motioned to the children to go back ot the other side of the road, but they did not.

The truck was carrying about 75,000 pounds of mulch, and the driver was unable to stop the vehicle in time. No charges will be filed against the driver.