Would you?

Would you call the cops if you saw that someone left their infant alone in a car? I feel like i should but my sister said to mind my own business. The car next to us in a parking lot of a grocery store has the keys in the ignition and it sounds like the radio is on but the car is not. Windows are rolled up and the baby looks to be maybe a month old in its carseat, covered with blankets. Ive been here at least ten minutes and no one has come out for the car.