2 Things
1. It was a hi-jack (transponder turned off, no Mayday), and the plane was not under the control of the pilots. It flew to wherever was demanded, and something happened thereafter causing it to crash, probably from an effort to regain control (as with United 93 during events of 9/11). So it could be anywhere. An eye-witness will eventually come forward.
2. The most fearsome worry to come out of this is how come an aircraft can invade national territory without military or civil or satellite detection? This leaves a hole in the defense systems of all countries.