Police in Knoxville, Tennessee, tell The Knoxville News Sentinel Alisa Hall left the 9-year-old alone in a 1993 Ford Taurus with the keys in the ignition while she stopped into a library.
Elizabeth Silvey and her 6-year-old daughter passed the Taurus just as the 9-year-old put the car in drive and hit the gas.
Children's services were notified but no charges have been filed.