Kids in CarsI saw a video this morning about what to do when you see a kid inside a locked car with no adult around. Because it takes five minutes, I'm going to save you about three minutes and summarize it for you.
First off, you don't have much time. The temperature in a car can rise over 20F in five minutes. Locked cars parked in sunlight can reach temperatures of 170F, incredibly.
Babies and small children aren't able to regulate their body temperatures as well as adults, so they're basically helpless in a situation where temperatures are rising rapidly.
Here's the important part. If you need to break a window (and if you can't find the parent immediately, you might well have to), don't waste your time pounding on the center of a window. That's where it's strongest.
Instead, run to your car and get a tire iron. Go to the opposite side of where the child is sitting. Hit the window where you see the red dot below:
That corner/low spot is the weakest part of the window. If you hit the window in the center with a tire iron, it will still take many attempts before the window breaks. If you hit in the very low corner as illustrated, you can do it with one or two swings, usually.
I haven't seen anything about kicking in the window, but if there's no tool or anything else available, at least aim for the correct spot to give yourself a better chance.