Automatic Transmission Park/neutral Start Switch problems of the 1999 Buick Regal

While parked in a driveway with engine off, with a 7 yrs old child in vehicle, vehicle roll out of the driveway into a neighbor yard and hit a tree. Child was without injury, and the gear shift was still in parked position. Dealer was notified, and replaced transmission interlock system. Provide any further information on this matter.