Intelligence officials are carefully analyzing the video released by ISIS that purports to show the mass beheading of 21 Egyptian Coptic Christians who were previously kidnapped in Libya.

In the video, a masked terrorist who leads the beheadings addresses the camera in North American-accented English.

"All crusaders: safety for you will be only wishes, especially if you are fighting us all together. Therefore we will fight you all together," the man says. "The sea you have hidden Sheikh Usama Bin Laden's body in, we swear to Allah we will mix it with your blood."

The Christian men are then laid face-down by the masked terrorists and simultaneously beheaded.

Heather Nauert reported on "Fox and Friends" that officials are dissecting the masked man's speech pattern and his facial features. They say this information may help them nail down his identity.

Nauert added that the man is believed to be an American with some Arabic influence.

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The militants had been holding 21 Egyptian Coptic Christians hostage for weeks, all laborers rounded up from the city of Sirte in December and January. It was not clear from the video whether all 21 hostages were killed. It was one of the first such beheading videos from an Islamic State group affiliate to come from outside the group's core territory in Syria and Iraq.

The Egyptian government and the Coptic Church, which is based in Egypt, both declared the video to be authentic. The killings raise the possibility that ISIS, which controls about a third of those countries in a self-declared caliphate, has established a direct affiliate less than 500 miles from the southern tip of Italy. One of the militants in the video makes direct reference to that possibility, saying the group now plans to "conquer Rome."

In a statement released Sunday evening, White House press secretary Josh Earnest condemned the purported killing as "despicable" and "cowardly," adding that the group's barbarity "knows no bounds." The White House statement did not refer to the hostages as Christians, but only as "Egyptian citizens" and "innocents."

"ISIL's barbarity knows no bounds," said Earnest, using another acronym for the terror group. "It is unconstrained by faith, sect, or ethnicity. ... This heinous act once again underscores the urgent need for a political resolution to the conflict in Libya, the continuation of which only benefits terrorist groups, including ISIL. We call on all Libyans to strongly reject this and all acts of terrorism and to unite in the face of this shared and growing threat."

The video's makers identified themselves as the Tripoli Province of the Islamic State group. A still photo, apparently taken from the video, was published last week in the Islamic State group's Dabiq online magazine -- indicating a direct connection between the Libyan militants and the main group.

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