I would think that an OWS type would've chosen a different target. They don't strike me as that type, BH. I would expect something more of a corporate related target than the Boston marathon. They've never shown themselves to be particularly violent, as far as I know. That huge bronze statue of a bull in Manhattan would be more their speed.
My guess, since we're spitballin' here, is that they are some crazy gun rights, anti-tax, anti- government, anarcho-redneck type. They sure have been wound up by the likes of lil' Wayne and shit fer brains types like Louis Gomert.
I dunno if they look like the typical muslim extremist type. Could be though. We'll see what happens when and if they track them down. My guess is that they are holed up somewhere in the U.S., otherwise the FBI would have already known they had left the country, unless they swam to Canada or elsewhere....