1996 geo metro lsi 4door transmission problem?

I was driving up a mountain while my car didn't seem to have enough power to climb. the car an automatic so i put it down in low and car made a popping sound and wouldn't go anywhere so i rolled my car back and all my transmission fluid and laying on the ground i never hit anything. at frist the car tryed going but the gears sounded like they were trying to go in place but after a sec no matter what gear i tryed it just acts as its in neutral. i have no clue bout car. please let me know if you think you know what it may be. thanks you