Witnesses described him as Caucasian, apparently; the MI driver's license had a non-MI address, which would tend to indicate it was produced in Europe, since no self-respecting American paperhanger would make such an elementary mistake.
Iran seems pretty likely as at least the sponsor of it, the Israelis have been knocking off Iranian nuke personnel with some success for awhile in their own black ops, it's no big shocker the Iranians would hit back at some point.