Washington (CNN) Shortly after the ISIS recruit known as Jihadi John was unmasked as Mohammed Emwazi of London -- outgoing U.S. Attorney General Eric Holder vowed, "Anyone involved in the killing of American citizens will be held accountable. It doesn't matter where you are, we will find you. We will hunt you down."

Holder would not confirm in an interview with CNN's Justice correspondent Pamela Brown the suspected terrorist's identity or reveal whether the U.S. government knows where "Jihadi John" is -- but he insisted America will not relent in bringing to justice the man seen in ISIS videos showing the beheadings of U.S. hostages and other Westerners.

"Whether it's through the use of our military or the use of our law enforcement capacity, if you harm Americans it is the sworn duty of every person in the executive branch to find you and hold you accountable, and we will do that," he said.

Holder, who will be leaving his post in the coming weeks, sat down for an interview with CNN at the U.S. Department of Justice headquarters Thursday in Washington D.C.

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