This is a fairly accurate idea of what I was expecting:

Obi-Wan: A young Jedi named Darth Vader, who was a pupil of mine until he turned to evil, helped the Empire hunt down and destroy the Jedi knights. He betrayed and murdered your father. Now the Jedi are all but extinct. Vader was seduced by the dark side of the Force.

Slaughtering younglings, was a "hunt"? I mean that bit of Obi-Wan dialogue sets certain expectations, some of which were changed in Empire and only partially demonstrated in the prequels.