I am currently doing my husband's genealogy and I've maybe got good news for you.Johnathan B. Donaldson, a civil war veteran is my husband's great grandfather.He is buried at Arlington National Cementary.Ironically, he served on the Union side but is buried in the Confederate section at Arlington.
He did commit suicide.I was able to find a copy of his obituary at the Washington Post.You can find his obit in the historical files of the Washington Post (1877-1954), posted on May 9, 1907, ProQuest Historical Newspapers The Washington Post (1877-1991) pg 2.
My Mother-In-Law told me about the Indian Heritage but that was over 20 years ago and she has since passed on to her reward but that was on her side of the family.
So far, I've found out that he had a son, Floyd W. Donaldson with Mary Randles.Johnathan also has a "Veteran" file which I located at the National Archives in DC. His certificate Number (Department of the Interior) is 544907.
It would be nice to share information regarding the family tree if you would not mind.Thanks for posting.