Who is behind the Boston Marathon Bombing? Update: Suspect arrested, found via videos...

Security in Boston and elsewhere is increased as investigators hunt for clues at blast site...

Update: 
Breaking:  Suspect arrested!  Found via videos.  More from CBS.  
Dark Skinned Suspect?  Chris Matthews just lost his tingle.  Unlike Sirota and Matthews, I care far less about the color of a terrorist, than his rapid arrest, prosecution and punishment for his evil acts.
Viral Read:  Arrest may be pending but suspect in custody...
Breitbart:  Arrest immanent...
Is this the suspect? No one seems to know right now...
Gateway Pundit:  More photos of possible suspect(s)?
Viral Read: Are these the bombing suspects?
Legal Insurrection:  Actual suspects or just guys in the crowd?  We will find out soon enough I suppose.
Wretchard/Belmont Club on the Fog of Media Coverage...
TOM: We got him...
The Brothers Tsarnaev had illegal guns.
What we know and what we don't know...
So how was this missed?

The Saudi National who was questioned appears to be cleared as a person of interest in the Boston Marathon bombing. [However this "innocent" suspect may be deported and the Saudi ambassador and Obama met unscheduled--what is up with that?]  Pakistan Taliban denies involvement.  So who is behind the attacks?

Jeff Goldstein makes an important point. The coward(s) behind this attack will be identified and punished (and all people of good faith want that). The shameless attacks will not be forgotten.

Update:
Circuit board found, may have been used in the bombing.
Where is the trail going?
The wait for a name...
Belmont Club and the "Runway Word"  I admit I prefer this to be imported Islamic terror (not because I want to blame Muslims as a class) only because the thought of homegrown attacks like this make me sick(er) and the obviously reality that Jihadi terror relies on such attacks all the time (so it is a fair assumption).  I do not want it to be domestic (regardless of ideology), only because I know the impact that will have on civil liberties.  And if it turns out to be some Occupy Wall Street or leftist group, I will not blame all liberals for it (but I will remind them that is the case).  And I resent the left attempting to blame all conservatives/republicans when some fringe group does something criminal.  I reject all criminals and terrorists.

Pictures showing suspicious package just before the blast?

AoSHQ with post and links...
A ricin postive letter sent to Senator Wicker (R-MS)?
TOM:  Hurry up FBI so we can start the media blame game...
Experts skeptical about homegrown terrorist group...
Glenn Reynolds and Media Bias (in how stories are covered and what stories are covered)
Gay Patriot:  Why are we not united as a nation over this attack?
The New Feminism:  Mamas don't let your babies grow up to be converts...