Here’s an article from that morning about the National guard presence. They are sneaky;
http://www.dvidshub.net/news/105211/massachusetts-national-guard-supports-117th-boston-marathon
I noticed the VERY FAST presence of soldiers removing the broken barricades so as to get to the injured people.
The soldiers had just finished a memorial hike for their fallen comrades - walked the marathon route with 40(?) lb. ruck sacks - started at 4 am or something!