Sophie Miller said the he is "is an excellent whistler"...they showed us the sheriff McCallister whistling in that right moment, but in the same episode we've seen Ray Haffner whistling too...I have three possibilities thought...Haffner,McCallister,Bob Kirkland...I'll watch all 29 (plus that ones of this season)Red John's episodes till 17th of november when there'll be the episode "Red John"