The battle in itself seemed tragically normal. Two Syrian opposition groups fought and there were heavy casualties on both sides. Then victorious rebels rifled through the pockets of the dead. One contained about $800 in cash — and an American passport.

Douglas McAuthur McCain, of San Diego was killed over the weekend fighting for the Islamic State of Iraq and Greater Syria (ISIS), according to the Free Syrian Army. Photos of McCain’s passport and of his body — which feature a distinctive neck tattoo — have been seen by NBC News.

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