2006 Saturn Ion AC not working.

Last summer my AC worked fine, I decided that I wanted to add refrigerant to it to make it cooler since it was too hot in my hometown. My brother in law put the whole bottle of refrigerant in to it when I turned the car on the air started to come out HOT! It doesn't come out hot anylonge, it comes out warm.
I had a mechanic look at it today and he said that is either the compressor or that it needs refrigerant, is this true?
Thank you very much!