When officers got there, they said they tried to save the boy and rushed him to a Charlotte-area hospital, but it was too late.
"I know the baby was worked on all the way up to the hospital," police said.
The Mecklenbug County Medical Examiner's Office said the child died from hypothermia due to environmental exposure.
Temperatures climbed into the mid-80s the day he was found in the car.
It's still unclear exactly how long the baby was in the car, but investigators said it was for "a prolonged period."
Detectives talked to family members and are checking surveillance video at the shopping center.
Advocates for children are warning other parents to learn from the tragedy.
"Parents say, 'How would you forget a child? This would never happen.' So, they don't create a system to protect from it, because they don't think that it would ever happen to them," Janice Williams with Safe Kids of Charlotte-Mecklenburg said.
The Division of Social Services said it usually investigates cases such as this one to determine if there was a pattern of neglect and if the woman’s other foster children should be removed from the home.
The Division of Social Services is investigating the case.