Warren was one of Osiris's victims.
30 years ago, he murdered the owners of a store, and went to prison for it. When he got out, he hit a bar, where he was grabbed by Osiris and put on trial, and was found guilty. As he ran, he was nearly run over by Sam and Dean, who quickly offered to help him. He told them his tale, and drew the symbols he saw in the barn where he was tried. Before Sam left to investigate, he told Warren to stay inside the ring of salt for protection. Warren ran away when he became too afraid, however, and the ghosts of the shop owners killed him.