It looks like the picture was taken by the soldier memorial at the Little Big Horn.
Brave Bear was an interesting character. I am remebering this without checking the details, but I think that somebody (Wannamaker?) offered a cash reward for the name of the Indian who killed Custer. At the time (c.1910?) the Indians were still worried about retribution, but the Cheyennes got together and Brave Bear volunteered to be named as Custer's killer, whatever the consequences, so that the tribe as a whole could benefit from the cash. At least, that's the story that I heard.
Yes, I read the same story,except that Brave Bear was at first not very anxious but stepped forward in order to get the reward for his people and "ready to face the consequences" which happened to be only stares and handshakes... the story is repeated, among others, in "Son of the Morning Star" by Evan Connell.