Dog was tracking Kellog, not Shawn, (by the way "Shawn" gets even more confusing later. . . you can sort that out later)
As for Kellogg, you get something from him fairly quickly that's kind of a clue as to why he looks that way. And then you get something a bit later that is an even bigger clue when you find "Shawn".
Lets just say there is a reason why I use "Shawn"
later on down the road they make mention that things have been "done" to Kellog