My steering wheel became very hard

So I drove up to Pasadena today then came back and stopped ay the grocery store and everything was ok. Went to work right after and 15 minutes later I come out to my car to leave and when turning it on it felt and sounded weird for a moment. I turned it off and tried again and it was ok but when I was trying to turn the steering wheel it was very hard. Luckily there's a mechanic next store and my mech. said it might be the power steering wheel gave out. The fluid is good. I just want to know if any of you guys had this problem out of nowhere and what was the outcome and part it needed. I looked through the forums and didn't find anything so I gave up looking. Any help would be appreciated. Thanks in advance.