Iraqi Kurds head off to help Syrian brethren against ISIS. (CBS News/Twitter)

McCain was being tracked by U.S. counterterrorism investigators long before his death--his travels closely monitored--as someone who was under suspicion of having joined a militant group.

He isn't the first. Abu Hurayra Al-Amriki "the American" was another American who joined ISIS during Syria's three-year civil war, radical Islamists claimed in an online video and over social media in May.

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