This will put me at odds with many of you but I think it's a combination of the fact that this area was remote (which is why there were no helicopters or reports "on the scene" immediately and there were only small press reports.
I think another reason though is the fact that it wasn't white kids. (see Jon Benet, Columbine and the intensive coverage that ensues)
Or, it could be that tribal police shut the res down, which IS what happened.