A runaway truck has been seized by police after it tipped into a front garden on Sydney’s north shore killing a 30-year-old mother who was holding her four-year-old son.

About 5pm on Wednesday police were called to a house in Wahroonga, following reports a truck had rolled down a driveway and tipped over, trapping a woman.

The 67-year-old driver wasn’t in the truck that was carrying rubble when it rolled backwards down the driveway on Spurgin Street.

Paramedics tried to save the woman who was trapped under the truck but she died at the scene.

Her son suffered facial injuries and has since been released from Royal North Shore hospital.

The driver was questioned by police for many hours and has been released.

His truck has been seized as investigations continue.