The mother allegedly told police she thought it would be fine as she'd left the a/c on, but investigators believe it had shut off after an hour, with the baby's internal temperature at 107 degrees when he reached the hospital.

They were strapped in their car seats. They couldn’t even get up to save themselves. She literally locked them in their car seats and shut their doors,” the boy’s grandma said.

A baby died after his mother left him and a sibling, 2, inside a car while she was getting a cosmetic treatment, police say. She's been charged with involuntary manslaughter.