When Todash called me and mentioned the bombings, their location, and the event that was occurring (I was learning about doggy play groups and their uses with shelter dogs and hadn't heard) I instantly said it sounded homegrown.
Patriot's Day seems to be specific to Boston (I may be wrong), so I suspect it's some disgruntled loony who is either native to or living in Boston wanting to make some statement or another.
This has a very homegrown feel to me as well, as if someone wanted to, ahem, "start a revolution" on Patriot's Day (the shot heard 'round the world, ya know?), but of course it might well be one perpetrator who simply wanted to cause destruction without a political aim.
Here is something different about this attack that doesn't seem to apply to previous ones (foreign or domestic): there's nothing governmental about the Boston marathon. It is not a Federal building. It's nothing to do with the government. It's a celebration of human achievement. That makes the bombing especially repugnant, I think. It's a strike against ... what? People who achieve a lot through hard work?
I hope they find the guy, whoever he is, and I hope that when the coward goes to shoot himself as they close in, his gun refuses to fire, first, so the complete truth (or as close to it as we can get) comes out, and second (because I am not entirely above being vindictive), so he can rot, rot, rot in prison, with no hope of freedom, EVER.