I kinda wonder if "Sylvester" was injected with arsenic to kill him, then dumped out of the wagon, where he was then found some weeks or months later.
He looks like he was holding something when his body was placed in its final position. Whatever lead to his death is hard to say but I dont think he was dumped. If his corpse was dumped fresh the arms wouldnt be in that position and if someone took care of the fresh corpse to arrange his arms then I doubt they would have dumped him once rigor mortis had set in.