I assumed you had already seen that, they're pretty much on top of things over there.
One thing that occurred to me is I hope these idiots were dumb enough to have cellphones on them at the time and leave them on. It would take the FBI awhile but they could eventually track them down that way. They may only end up with a pay as you go phone from a retailer, but maybe they could get a few more images of these guys and some other details could turn up as well. Better yet if that was the remote for the bomb, pretty easy to trace the exact call at the time the bomb went off. I'm sure they would have already done that had it been a cellphone trigger though.