The only remote possibility I could come up with, was a William S. Turner found in the Ellis County Death Records. I don't think that is him, because it is so far away. And there was no date. If Julia Ann died late enough for there to be one, I'd order her Death Certificate from the Oklahoma Health Dept. Vital Records Division. You can get an order form from Oklahoma Genweb. Is your Riley Keys the one showing up on the 1838 Cherokee National Council?