Pressure cooker bombs have been around for some time as you say. The technology is widely available on the internet.
This style of bombing attack, the loose Saudi connection, non-government target, big crowd target, smacks of AQ.
This style of bombing attack, the loose Saudi connection, non-government target, big crowd target, smacks of AQ.
Islamist or anarchist seems most likely. Patriots Day event would make a good target for an occupy/anarchist nut. Then again it could be a screw loose Eric Rudolph type also. Anything possible at this point.