My source is military photos.net. This DEVGRU operator was performing bodygaurd duty to this political official just before president Karzai was assasinated. This makes me wonder why you suspect this guy to be someone else since bodyguarding is a specialty of DEVGRU.
What source, exactly, do you have telling you that this guy is a member of the Development Group? I'd say he's not, for a few reasons that I'm not going to take the time to post here. I would bet, though I certainly can't be sure, that he may be a FORMER SEAL or even DevGru, but that now he's working as a security agent for Blackwater.