Good sign, likely because someone had broken the window before because of a "dog in need" type situation. People will do anything to there peoples property if they feel like the need is urgent. Especially in hot climates, hot times of the year, there are PSAs all of there the place about not leaving your pets in a hot car.
Around here the police K9 units have special engine start-stop devices designed to start the engine if the temperature gets too high or low, and if the temperature doesn't fix itself from starting the engine, the device will automatically roll down the windows (these were all installed after the highly publicized death of a police dog from overheating in a car). These cars also usually have the rear windows partially open, and I think they have fans mounted in those windows too.