Yesterday fluid went EVERYWHERE. The car won't shift into gear at all. Ideas why

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I had the oil changed and transmission fluid levels checked. I drove it approximately 10 min. to a gas station. It would not shift into gear going on a slight incline into the station. I had to put it into park to keep it from rolling backwards. Fluids kind of a reddish brown but not as thick as oil were ALL over the ground beneath it.