I have seen video before the one they are showing.
The boys were chanting "CCH" which I believe is their High School.
The Native American saw the boys sitting some standing on the steps of the Lincoln memorial.
Next he starts singing and walks over to the boy and the photo.
Next the boys join in the chanting of the Native American.
I think the Native American was trying to get them to leave, but he failed.
Libtards have twisted the story to make it seem like the boys came up to the elder and started to mock him.