After U.S. officials confirmed earlier this week that 33-year-old San Diego resident Douglas McCain had died fighting alongside Islamic State militants in Syria, the State Department says it's looking into a report that a second American was also killed there.

NBC, citing an anonymous source, first reported on the second American jihadi, and State Department spokeswoman Jen Psaki says officials are aware of the report and are "looking into it."

Earlier this week, the U.S. confirmed that McCain, who reportedly grew up in the Midwest before moving to California and at some point converted to Islam, had been killed fighting with the Islamic State in Syria.

CNN writes:

"McCain grew up in the Minneapolis suburb of New Hope, his friend Isaac Chase said."The two lived in the same New Hope apartment building and became fast friends." 'When I first moved here, I didn't know anyone, so I went to the park and I would see him and his brother and a bunch of other people playing basketball, and he asked me if I wanted to play,' Chase said." 'We just hung out pretty much from 10 o'clock in the morning all the way until nighttime. We'd just play basketball and talk. ... He was an older guy that I looked up to. He was actually a good dude.' "

If confirmed, the as-yet unidentified second American who died fighting with the al-Qaida offshoot would be the third U.S. citizen to be killed alongside extremists in Syria — Mohammad Abu-Salha, also known as "the American" by his fellow jihadists, was killed in a suicide bombing in May.

Caitlin Hayden, a spokesperson for the National Security Council, said: "We continue to use every tool we possess to disrupt and dissuade individuals from traveling abroad for violent jihad and to track and engage those who return."

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