For those of you who are willing to consider that this could be a 'false flag' attack,
there is detailed analysis of photos and videos here
Boston Marathon - alleged "terror attack" - April 15, 2013 ? Cluesforum.info
I can clearly see that many of you wont look because it is outside your comfort zone to consider the possibility that governments would inflict death and suffering on their own population.
So be it - I can cope with your angry responses if you choose to make them.