I tried a few times but always restored the quick save shortly after. I even found a spot, up toward the Jarl's palace where I can launch an arrow without being spotted by the guards (off the side of the stairs, on the rocks near the falls) and nailed a perfect long shot. I went down and took in his body, lying forlornly and unmourned, then restored.
The next time I was in Whiterun at night, I went into the house, turned into a werewolf, mauled him and left.
This is the coolest way to get him I've seen, though this isn't the best video of it: