Daily Mail - Boston Bomb
Police believe shrapnel consisting of metal fragments and nails was packed into pressure cookers and designed to look like discarded items.
Pressure cooker bomb is preferred weapon of al Qaeda, and was used in Times Square bomb attempt in 2010.
Authorities reportedly find circuit board that may have been used to detonate bomb.
Doctor says that numerous sharp metal objects were extracted from victims of the blasts.
Ok, I'm backing aQ affiliates as responsible.