There's an old legal truism that applies to situations like this: res ipsa loquitur, or the thing speaks for itself. The classic example is a barrel of flour that rolls out of the second story window of a bakery, crushing a man standing below. While one might not be able to point to the exact negligent behavior that led to the man's death, absent some negligence, in storing the barrels, securing the windows, or in transporting flour, he would not have been killed.
This seems perfectly applicable to the case of Ronald Sinvil, 36, who was crushed by a street sweeper. You've seen these vehicles. They move slower than a grandmother on a Hoveround. So how did such a slow moving vehicle manage to accidently run over a man who, minutes earlier, was asking his girlfriend for directions to her apartment?