OT, but I had a very similar experience to this. About three years ago, I was visiting my sister and nephew (1 yo at the time) where they lived in a suburb of D.C. One day, we ate at a restaurant in one of those lifestyle shopping centers where you can parallel park along the curbs outside the shops. We finished eating and got back in her car, and just as we were about to leave, we noticed that there was a luxury SUV parked just behind us. The engine was running and there were two very small children (between 2 and 4 yo) in carseats in the back. We were horrified that someone had not only left their children alone in a car, but also left the keys in the ignition for any would-be thief to drive off with them and the car. My sister and I stayed and kept watch on the car, debating about calling the police, when the children's mother finally returned, walking out of a pizzeria across the street. She noticed us looking at the car and asked us what was our problem. I told her that she should not have left her children alone in the car and we were just about to call the police, and she retorted that she had been gone for just a few minutes. When I also mentioned that she had left the car running, she looked at me as if I was an idiot and said that they needed air conditioning (duh). We just left at that point. I know we all learn new things every day, but I couldn't believe she thought it was o.k. to do that.
My mother's friend lost one of her two children when their babysitter left them alone in a running car while she went in to a store to get some ice cream. I will just say it was a terrible accident, and I have remembered that story for more than 20 years.