The FBI is now asking for the public's help identifying an English-speaking ISIS executioner.

Fox News chief intelligence correspondent Catherine Herridge reported today that, according to an intelligence official, biometrics and facial recognition technology was used to determine that the man is an American.

Officials believe he is from the Midwest, but are not ruling out Canada.

This would be the first American citizen participating in a mass execution by ISIS.

Meantime, she cited a senior State Department official's estimate that ISIS has five TV stations in Mosul, Iraq, and two in Raqqa, Syria.

The ambassador described it as a "Mt. Everest of radicalization" on social media, compared to a "foothill of counter-ISIS propaganda."

The U.S. government has now even coined the term "ISIS fanboys" to refer to those on social media who spread ISIS propaganda or retweet ISIS messages.

Watch Catherine's full report above.