DOLTON, Ill.—A 3-year-old boy accidentally shot his mother to death as the family was sitting in their car in a suburban Chicago supermarket parking lot, police said. The woman was shot Saturday in Dolton and pronounced dead at a hospital, police said. The family was sitting in their car outside a Food for Less store when the boy somehow found the gun and fired it, striking his mother, police said. Authorities said the boy’s father was in custody after indicating that he owned the gun. No charges have been filed as police continue investigating. The Associated Press left a message Monday seeing updated information from police. “This could have been prevented,” Dolton trustee Andrew Holmes said Sunday as he visited the supermarket to hand out gun locks and speak to shoppers about the importance of gun safety. “All it takes is a second: unlock it, thread it through the barrel, …