Yeah, a few weeks ago, I asked if we were going to experience an attack on our own shore.
The attackers: Had contact with people, both foreign and domestic, that the FBI claimed are suspected extremists. Destroyed all digital footprints the day before the attack. Left pipe bombs in their home.
Here is what the Obama camp wrote in 2008 on this and related issues, while he was running for the presidency (link is to download a .pdf of this letter): I think the New York Times spelled it out pretty well in this editorial: