I came across this while doing some research on Baker and Johnston. My first thought was that Crazy Horse's brother, Little Hawk, would not be known as a 'big' war chief and, as far as I could recall without looking it up, his death occurred at the hands of white men. The second thing that struck me was the red head gear worn by the victim. It could, I suppose be a stylised roach, but it struck me as an attempt to depict the red cloth headgear we'd been talking about here: amertribes.proboards.com/thread/1708/red-war-capes?page=1 - though, granted, he isn't wearing the red cape associated with this.
This made me wonder if it could be a reference to High Backbone, who was killed by Shoshones, who and who might be regarded as both a 'big' war chief and as a brother figure to Crazy Horse. Looking back through material to see if I could find more information, I noticed Tom Powers also thought this drawing might depict High Backbone's death in his excellent book, The Killing of Crazy Horse.
It's known Washakie painted more than one version of fights he was involved in and at least one of his sons (possibly Dick and Charles 18.104.22.168/museum/about/documents/handout_washakie..pdf)also illustrated his exploits. Just wonder if anyone knows more or has seen any of the other robes which might depict the same event...
It’s fascinating to know High Backbone’s death in 1870 might have been at the hands of Washakie. High Backbone was often depicted wearing a red ‘turban’ and cape, eg. by Amos Bad Heart Bull. While no cape can be seen here as you mention, the turban is unmistakable. I agree that from the text it could be concluded that the victim is indeed High Backbone, although it could be that Washakie merely counted coup and that someone else killed him. Can’t make it out clearly but it seems Washakie is wielding a coup stick, and the text is not conclusive on HB’s fate.