Loss of power steering

Power steering was making noise. We added power steering fluid. I was able to drive it with very little noise. A day or so later while driving I heard a noise, the dash lights dimmed and I lost power steering. I thought I was losing power but I was not. My husband thought the sound we heard sounded like I ran over something, I thought it sounded like a pop or snap. My husband was able to drive home (about four miles or so) but the lights kept getting dimmer. Under the repair section of this site it said if the power steering pump or belt went out the car would be non operational. What do you think it could be?