Very sad to know this, but yes there are many chances that these people are kohistanis because i have also visited this area in august and when we were going to Dharam sar lake, the driver told us the details, that beyond babusar top , in challas i gues ,army operation is taking place against the terrorists and the people who killed those nanga parbat tourists, the army and police got some clue of those people residing in challas and they killed those investigation people too, so now operation is taking place there, so all those kohistaanis moved into kaghan valley area in mountains and hid themselves there so it might possible it happened due to them