He was seeking refuge there because he knew there would be bloodshed and retribution. Since he didn't want to force his people to move into the reservation, some deaths occurred with white settlers who lived there and he knew that if they stayed, it would become much much worse.
Explanation: Phrenologists were largely pseudo scientists who attempted to establish a biological basis for differences between the races. This burgeoning science was used to buttress theories of racial inferiority.
