So, after many many many hours of completing the "Frost" quest and 12 Letrushes in the whiterun stables, the orc finally found letrush out in the wild and finally killed him. It was the most beautiful moment ever (wipes tear from eye). This was immidietly followed by a horrible massacre of the Louis Letrush army in the hands of Galmar Stone-Fist and the stormcloaks while taking over whiterun. I just stood back and watched. It was the most satisfying thing ever. Then I went to a previous save file and killed them myself.
I just hope they clean up properly as I would surely hate having 12 corpses lying around every time I go to whiterun.