[I got this video from livingonplanetZ on youtube.]
Eyewitnesses to both of the Boston Marathon bombs confirm that pyro simulators were used to fake the explosions. This shows how dramatic looking effects were produced without any danger to the waiting actors at the scene. Strategic Operations was the contractor admitting to working with the perpetrators within Boston government at the "Urban Shield" exercises, and was almost certainly involved in supplying the special effects for the Marathon as well. Compare the Strategic Operations effects with the physical evidence in photographs from the marathon and the accounts of eyewitnesses, and you have a perfect match.
This issue is taking on a new and even greater significance, with the revelation of the NSA massive spying operation against innocent US citizens. Many of the companies involved in 'security' at the Boston Marathon (in other words, setting up the terrorism) have considerable ties to those also doing the spying. No doubt, staging the false-flag bombing was meant to help "justify" the spying - as well as the huge amount of tax payer money they receive for doing it. After watching this, you will never think about the Boston Marathon bombing, FEMA, the FBI, or terrorism the same way again.