It can't be a surprise that the islamic state is having some of their people posing as refugees either way.
Just a quick two cents on that: supposing there was a passport found at ground zero of an attack, can it be inferred that it belonged to the attacker as opposed to:
--Someone trying to stop the attacker, who therefore ended up being at the center of the attack;
--Someone whose identity was stolen by the attacker, perhaps at an earlier date, perhaps after their own murder;
--Someone who happened to have been standing near the attacker and died;
--Someone who was near the attacker, panicked, and dropped it while escaping, etc.
I just thought it was important to point out that there are options other than "it was definitely the people whose passports were found" and "it was an inside job/false flag operation/mossad/etc."