Unmasking ratchets up hunt for ISIS executioner Jihadi John

The dramatic unmasking of the ISIS executioner known as "Jihadi John" last week makes the black-clad star of the Islamic terrorist group's grisly videos a marked man with a big price on his head, terrorism analysts told FoxNews.com.

Intelligence authorities in the U.S. and Great Britain have known the knife-wielding jihadist was 26-year-old Mohammed Emwazi for months. But the public identification of him, first in a Washington Post article, and followed by disclosure of a torrent of personal information about his life and associates prior to going to Syria in 2013, will turn up the heat and likely ensure he never leaves ISIS' so-called caliphate alive.

"He is a big target."

— Michael Harkins, former FBI agent

"British intelligence had a handle on Emwazi's identity for some time prior to the public release of the identity," said Mike Baker, a Fox News contributor and former CIA covert operations officer. "They've been working the target for awhile, mapping out his associates in the UK, understanding his motivations and path to radicalization and working with U.S. intelligence."

UK and U.S. authorities have been tracking Emwazi's digital footprint for at least five months before his identity was publicly known, likely monitoring every social media account and tapping into phone communications between the young terrorist and his associates, according to Baker.

Emwazi's role as the face of ISIS' gruesome videos, in which only his eyes showing through the slit of his black mask and his British accent offered clues to his identity, make him a high-value target. Even though he is likely not key to ISIS operations, he is a powerful symbol of the terrorist group.

Now that his name is known and his photo has appeared online and in print around the world, the noose could tighten quickly on Enwazi, who was born in Kuwait and raised in London. He will not be able to travel back to Great Britain, as Western intelligence officials fear so many foreign fighters could. Any communications with family or friends are sure to be monitored, and the pressure for someone -- even within the terrorist group -- to turn him in has been ratcheted up, say experts.

British Prime Minister David Cameron has vowed to use all resources necessary to hunt down Emwazi. On Sept. 19, the U.S. Senate approved - without knowing his full name - a $10 million bounty for information leading to his whereabouts. That bounty is a powerful incentivefor information, former FBI agent Michael Harkins said.

"There’s certainly now an incentive for someone to help the US government," said Harkins, who worked for 22 years with the FBI and who was deployed on numerous overseas operations.

"He is a big target," he said. "By getting someone like Emwazi, it sends a great message that no matter who you are, we’re going to find you and hold you accountable for killing U.S. citizens."

While Harkins and Baker could not detail specific tactics used by authorities to track Emwazi, money for information has proven successful in tracking high value targets in the past, including those of Jordanian-born Abu Musab al-Zarqawi, a leader of Al Qaeda in Iraq.

"There have been some major apprehensions as a result of a source coming forward seeking an incentive," said Harkins.

Emwazi's alleged ties to terror groups were well known to the British government. He was a member of a terror cell linked to failed attacks on London's Underground subway system in 2005, according to court documents.

In the documents, first published by two British newspapers, The Observer and The Sunday Telegraph, Emwazi is described as a "person of interest" to MI5, Britain's domestic counter-intelligence and security agency.

Authorities said he was a member of a cell formed in 2007 to recruit fighters for al-Shabaab, a Somalia-based terror organization linked to Al Qaeda. The network was believed to have at least a dozen members.

The BBC reported that Emwazi attended Quintin Kynaston Academy in northwest London and in 2009 graduated from University of Westminster with a degree in computers. Emwazi's father said his son was a devout Muslim and last spoke with his family in 2013, when he said he was going to Turkey to join a charity in Syria. Although Emwazi was born in Kuwait in August 1988, his family are so-called "stateless" southern Iraqi immigrants, many of whom were deported after Kuwait was liberated from Saddam Hussein in 1991.

Emwazi first appeared in an ISIS State video last August, when he beheaded American freelance journalist James Foley. He later appeared in videos showing the beheadings of American journalist Steven Sotloff, British aid worker David Haines, British taxi driver Alan Henning, and American aid worker Peter Kassig.

Although the United Kingdom-Muslim advocacy group CAGE attempted to paint Emwazi as a victim of harassment by British intelligence, a charge Prime Minister David Cameron called "reprehensible, Emwazi was long known to associate with radical and terrorist groups.