In case you have not thought about this already, let me frame the underlying context that the media will likely use to blame "domestic terrorists":
Where did this event occur? Boston.
What else occurred in Boston? The "Tea Party."
What was the "Tea Party" about? A protest of taxes.
What is today's date? April 15th... TAX DAY!!!
~Please excuse me for being "Captain Obvious"... I'm going on 26 hours.
All day I have heard the talking heads say everything from "It has to be these right winger extremist types" to the tongue in cheek "well this could be either foreign OR domestic".
Other things that I have heard was that Oath Keepers was having or at some event there in the Boston area. Also how this is the same time frame as other "domestic acts" such as OKC and Columbine. In my opinion the media is already casting the votes for the jury before the investigation is fully under way.
Another possibility is that should they claim it to be a foreign act they could use it as a pretext for more "Iraq/Afghanistan" like invasions.
All in all it has all the hallmarks and stinks to hell like a False Flag. Stay tuned and screen capture all websites/pics and record all audio/video you can!