Try to Locate the Pet Parent and
Go to security and ask them to page the person that owns the car.
the animal will often be dead or seriously injured.
If the animal is not already in distress and security is in easy (as in a minute or two) reach, ask security to find the owner. Then call 911 and figure out how to break the window if the owner doesn't show up right away. The moment you see actual distress, don't delay - save the critter.
Yes, some asshat could complain about you breaking their damned window. However, that life is worth the risk. Dying of heat stroke in an oven is a terrible way to go.