Definitely true about the American Indians owning black slaves. They even had a slave rebellion in Oklahoma back in 1842!
https://www.okhistory.org/publications/enc/entry.php?entry=SL002
The US Army almost caused another Indian war when it was decided to force the Plains tribes to adhere to the 13 amendment. Most of the freed slaves were from other tribes or Hispanics.
Not long ago the Cherokees threw many blacks off the roles.
http://hnn.us/articles/36394.html
But eventually the Cherokees took them back. Some other tribes, however, are still resisting.