One good example of pathos comes when Chris meets Ron Franz, an old man who feels an immediate connection to the wandering youth. Franz, who acted as a mentor for many young boys, felt so emotionally connected to Chris that he offered to legally adopt him, but Chris's philosophy prohibited intimate emotional connections and he refused. To Chris, this was another example of his ideals and the sacrifices he needed to make for his personal growth; to Franz, it was a rejection of their friendship at a deeper level.
...their burgeoning friendship also reminded him how lonely he'd been. The boy unmasked the gaping void in Franz's life even as he helped fill it. When McCandless departed as suddenly as he'd arrived, Franz found himself deeply and unexpectedly hurt.
(Krakauer, Into the Wild, Amazon.com)
Franz never saw Chris again, and the news of Chris's death came as a shock. In his last years, Franz adopted some of Chris's philosophy and traveled; in the personal interviews from the book, it is clear that he felt almost betrayed by Chris's rejection. The comparison between Franz's feelings and Chris's refusal even to contact his own family makes Franz's situation even sadder.