'Jihadi John': How he horrified world and emboldened extremists

This undated image shows a frame from a video released Friday, Oct. 3, 2014 by Islamic State militants. Mohammed Emwazi has been identified by news organizations as the masked militant more commonly known as 'Jihadi John.'

DUBAI, United Arab Emirates -- The Islamic State group militant known as "Jihadi John," who was targeted in a U.S. drone strike, horrified the world with his brutal beheadings of hostages. But his videos, with sneering taunts of the West, served as a recruiting tool for those drawn to the dark, bloody world of extremism.

Mohammed Emwazi's brown eyes peering out from a black mask and his London accent became the first contact many around the world had with the group, though the extremists carried out other mass killings, rapes and enslavements in their march across Iraq and Syria.

The reason was the slickly produced, sound-bite-quality butchery he and others committed before the camera. Their victims included U.S., British and Japanese hostages.

His first filmed killing was that of American journalist James Foley in a video released in August 2014. Tabloids soon made famous the moniker "Jihadi John," based on nicknames freed hostages said they gave their British-sounding captors, a reference to Beatles member John Lennon.

In some ways, the violence he committed was not new -- the dark horror of beheading videos haunted the Middle East before.

The Islamic State's predecessor, al-Qaida in Iraq, released footage in 2004 of the decapitation of American businessman Nicholas Berg. In the video of his killing, Foley wore an orange prison-style jumpsuit similar to the one Berg wore at his death.

But while the statement in the video of Berg's killing was in Arabic, Emwazi spoke English in his videos, making the message even easier for the world to understand. Born in Kuwait, Emwazi grew up in Britain, giving him added symbolic weight.

"You're hearing it in your own language so the threat sounds all the more menacing," said Raffaello Pantucci, the author of "We Love Death As You Love Life: Britain's Suburban Terrorists" and the director of international security studies at Britain's Royal United Services Institute.

"It speaks to the audience and says, you know, 'We are you. ... You think we're this alien thing but actually no, we're from within your very communities,"' Pantucci added.

After Foley's killing, Emwazi appeared in other videos of beheadings, including the mass killing of captive Syrian soldiers. In most, he acts as a narrator, taunting the West and promising an Islamic State victory, though the videos don't make clear if he carried out all of the actual killings.

Militant sympathizers uploaded the carnage to websites and shared them via mobile phone apps in a way impossible only 10 years earlier. That drew more people curious about the Islamic State's apocalyptic beliefs, inspiring some to join the militant's self-declared "caliphate."

Whether Emwazi was killed in the U.S strike in Syria remains unclear. He has been one of the West's top targets after Islamic State leader Abu Bakr al-Baghdadi and his other lieutenants.

President Barack Obama said America would "be relentless" in pursuing Foley's killers.

"When people harm Americans anywhere, we do what's necessary to see that justice is done," Obama promised.