thats not the important part, the importance is that they knew we would be running "drills" at the same exact place and time, and were able to execute an attack that looked just like our drills to the point it's blown into a huge conspiracy tearing our nation apart...
DHS has already came out and admitted they were doing drills at the marathon involving backpack bombs..
http://www.redicecreations.com/article.php?id=25582
http://www.activistpost.com/2013/06/dhs-admits-backpack-explosive-drill.html
this isn't tin foil hat stuff, this is only facts... scary ones..
it means we have an even bigger leak somewhere.. someone is either pulling both sets of strings... or, there really is a terrorist org so infiltrated they know where and how, and when, we will pull off top secret training drills... and that's where they attack. to blend in.