Robert Mosby was found dead in his cell at Powhatan jail on May 10, 1901. He had hung himself with his bed sheet. Mosby shot and killed his wife about a week prior to his suicide. His wife died the next time from her injuries. She had refused to move with him to the Black River area.
Source:
Arkansas Democrat (Little Rock, Arkansas) · Fri, May 10, 1901 · Page 7