I too am having second thoughts on a lone wolf doing the entire setup as more information comes in.
We all know there are "sleeper cells" throughout the world, and who they are obviously is unknown for the most part. Because of the great strides Islam has made into many countries and into political positions I doubt those infilitrating the rank and files of governance would have their fingerprints on this...too risky...so they would farm out the nasty work to others....pending on where this whole thing began. It had a starting point...and there were warnings for awhile this might take place...although I doubt any suspected the slaughter on the Island.