Vehicle was parked in driveway and put into park. After getting out of vehicle and walking into house we noticed the car started to roll forward and by the time we could react the car was picking up speed and rolled into a tree at the end of our driveway. A few days prior while driving 40 mph near our house the car inadvertently went into neutral without notice and without switching the gear shifter and we had to put the shifter back into drive while moving.