Katie Luong's daughter, Gabriella, was found unresponsive in the back seat of the family car three hours after Luong went into the family business in Homewood.
Luong, 31, said, "I want to tell everybody that I wish I was in that car seat, not her," The Birmingham News reported Thursday. "If I had to die for her to live, I would have done that."
At the time Luong realized she had left her baby in the car Wednesday afternoon, the temperature was about 90 degrees. Authorities said the temperature in the car was about 127 degrees.
Luong said she forgot to drop Gabriella at the babysitter because she was distracted by thoughts of an employee who had killed himself the week before and plans for her child's first birthday party.
When the babysitter called about 1 p.m. to ask about the baby, Luong said she realized what had happened and ran out to the car and found Gabriella unresponsive.
A witness said the mother panicked, ran over to the car and began performing CPR on her daughter, NBC News reported.
Paramedics took the child to Children's Hospital, where she was pronounced dead on arrival, WVTM-TV, Birmingham, reported.
A San Francisco State University study found at least 21 children have died this year nationwide after being left unattended in vehicle, NBC News said.
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