He was visiting the city of New Reno for drinks and girls, but unfortunately, the citizens of New Reno did not tolerate ghouls. Willie was taken to Golgotha and buried alive, with a headstone calling him "the dumbest son of a bitch ever to set foot in New Reno."
The Chosen One can dig him up from his grave with a shovel, without getting the Grave Digger reputation. Willie will then complain about how long it took to dig him up, and starts to walk away, muttering insults about his fate.
Having Lenny in-party reveals that Willie was actually Lenny's father. However, he has nothing to say to his son, as he is not in a mood to be talking.
After walking out of the map, he will disappear permanently, claiming that he has got places to go.