He had battled addiction throughout the final years of his life, but toward the end, he cleaned himself up and became a born again Christian. It appeared that he had turned his life around until his nephew Chavo Guerrero found him unresponsive in a Minneapolis Minnesota hotel room. When paramedics arrived on the scene, he was pronounced dead. I remember that as being one of the saddest days I had ever experienced as a wrestling fan.
I still watch the Youtube video from the next night's Monday Night Raw where WWE Superstars paid tribute to Guerrero with a 10-bell salute. Here is the link to the tribute, in case anyone was curious.