If they are with a federal/state/local agency and are monitoring a large public gathering, great. If they are not monitoring, then why are they there?
If the are not with any federal/state/local agency then who are they? Why are they there? What are they doing? Who sent them?
They very obviously are not civilian. What is going on?
I wouldn’t be worried about them right now. Here’s the guy to concentrate on ...
“New, Higher-Resolution Image of Boston Marathon Suspect Emerges”
https://www.facebook.com/GW.IFA/posts/606678846027436