car won't steer left or right

What is your question?

While driving about a month ago, taking my wife to work, i heard a "SNAP" sound then I started to lose power and it was difficult to even steer the car. I was able to get it pulled over and I popped the hood with the motor still running trying to see if something had gotten caught up in the serpitine belt but iI didn't see anything. But when I cut the car off, I was unable to restart the car. I had it towed and the shop said I needed a alternator but the car was running fine before then so I didn't want to pay for something I didn't need right then. When they brought the car back to my house, i noticed that the car came on, I just couldn't turn the steering wheel. It could only go forward and reverse. I don't know what it could be. The power steering fluid reservoir was still full. So I don't know what else it could be. I could use a lil help from everyone thanks.