Briton and a person whose nationality was not revealed. The news outlet said Thursday the three had been fighting alongside the rebels and were found with weapons. The report said they were ambushed in their car in the flashpoint province of Idlib in northwestern Syria, where government forces have been battling rebels for control. TV video showed a bullet-riddled car and three bodies laid out on the ground. It also showed weapons, a computer, a hand-drawn map of a government military facility and a flag belonging to the al Qaeda-affiliated al-Nusra Front. The United States is aware of the report of the reported killing of the American and is working through the Czech Republic mission in Syria to obtain more information, a State Department official, speaking on condition of anonymity, told CNN. Citing privacy concerns, the official said, We are unable to comment further. Pictures circulating on the Internet show the body of Nicole Lynn Mansfield, 33, of Flint, Michigan, her father and daughter told CNN on Friday. The UK Foreign Office confirmed that a British national was among the dead. Their family has been informed and we are providing consular assistance, it said. Kerry, the top U.S. diplomat, said that some 1,500 to 2,000 American fighters may be in Syria. It's hard to get a peg on the exact number, he said. American's family: She went to Syria to help