Odds are better than even that the bombers are Chechens , who are not only Islamic but an ethnic nation that bears grudges from mistreatment at the hands of Putin, Stalin and Peter the Great.
I think it is interesting that the Chechins are still fighting in spite of generations of negative results, it is as if Geronimo and his kids and grand kids were still shooting .
There is an old saying "they can't kill us all" which the Chechins seem about to prove false.
