My tires got stuck in the snow last night

My tires got stuck in the snow last night. I had someone try to push me out and then I had a truck push me back into the driveway I first got stuck trying to get out of. Once I got back into the driveway, I could not turn my steering wheel at all. I filled my power steering fluid and gave it a moment then drove back to work. After I got there, the steering wheel would not move again. There is no whining of anything, the steering wheel will just not move, or barely move. What could it be?