The authorities have a vested interest in finding that the mastermind was not a Syrian refugee. So he’s Belgian.
But at least one was a Syrian refugee, see http://www.freerepublic.com/focus/news/3360778/posts?page=10#10
The team behind this attack (or series of attacks) were Islamist immigrants living in France, Belgium, and Germany as well as some who’d traveled from Syria.
Europe is already infested with a malignant subculture, they are just importing more.
And the terrorists proclaimed at the concert that the attacks were motivated by Frances attacks on Syria so yes, Syria is at the root of this matter but if it wasn’t that, they’d find some other excuse. Just as Nick Berg was not kidnapped and beheaded because of Abu Ghraib, he’d already been held hostage for a month and another captive had famously escaped that week. He was a liability and Abu Ghraib gave them a window to proclaim moral equivalence to the liberal Left.