Help with artist name/thoughts on unusual painting of Indian fighting indian

This painting hangs on the wall of my friend's 2nd hand/thrift store - next to a shelf full of buddha & indian figures (I'm not sure what country he & his wife are from, I do know it's not Cuba, but it is south or central America - and they like my other Cuban/ S. or C. American friends all have something like this for luck - 1 has a 6ft Indian figure at the door of his store).
I asked him if he would sell it to me because I thought it was different - Indians fighting Indians instead of the usual Indians fighting cowboys - I started at $25 and went all the way up to $100 with each "No, Charlie I don't want to sell it" (each no made me want it more!).
Yesterday I told him I'd try to find out more about it for them (they have given me some incredible deals so it was the least I could do - besides I want to know too!) and knew just where to ask...so here I am!
Any idea of the artist? (I think that's John something?)
Any thoughts on the painting I can tell them?
Thank you for your help!

 

I dont think you will find the artist on this as its done by a amateur.

 

It might be a copy of something better known.

 

Charles Russell's 'When Blackfeet and Sioux Meet.' 1908.

Debora

 

Debora you are amazing!