Blood and Gold

An elderly woman is murdered in front of a large safe in her home. Clint finds how to open the safe just as Sergio comes in to say there was a lot of blood on this one. Clint is dstaring into the safe, which was filled with gold bars. He says there was a lot of gold. Where did it come from? How did she get it? She was obviously killed for the combination to that safe, and as obviously didn't tell it. Who? What was her past story?