According to Chapter Six, why was Shawn upset as he tells to Buck? What does Buck do to comfort him?

As he says to Buck, Shawn was upset because a member of the Dark Suns who he grew up with came up to him while he was getting soap for his mother’s eczema and told Shawn he should not be in the area. Buck tries to tell Shawn to let it go, and when Shawn can not, Buck gives Shawn his gold chain as comfort.