Many attacks in the US have been facilitated by the FBI. What? Yes, our FBI will often times continually drop ideas into the heads of these people trying to bate them in to action. Often times the FBI has fueled the already burning mindset of a would be attacker, set them up with the props needed, led them to FBI informants, and given them the needed info to carry out plans that are often times fed to the by the FBI.
You can find more through a Google search, but here is an article and several good links through it to back up the claims. The FBI is not always being the good ole' boys in there attempts.