A New Hampshire woman is facing possible child-endangerment charges after her 7-year-old daughter accidentally ran over her 2-year-old sister. Police said Thursday that the accident happened Tuesday night, when the woman let her 7-year-old daughter start the family’s car. The girl started the car but reversed it into her little sister, who was seriously injured. “I saw the baby trying to open the door and it wasn’t opening, so she was going behind the car and the car was going back and it hit her and she got hurt really bad,” a witness was cited as saying by CBS News. The car only stopped when it crashed into a neighboring motor home. Police said they believe the mother, who was not identified, had previously allowed her daughter to use the vehicle. “What makes this even more frightening is that this was 100 percent preventable,” Salem Police Capt. Joel Dolan told reporters.