How did "Jihadi John" slip through the cracks?

LONDON -- The day after the true identity of assumed ISIS executioner "Jihadi John" was revealed, some very important questions remain unanswered; the first and foremost being, where is he now and how and when will he be brought to justice. The answers to those may still be some way off, given the chaos in northern Syria and parts of neighboring Iraq where ISIS remains firmly in charge.

But of equal, if not greater long-term importance, the British government needs to answer questions about what drove a boy from West London to become the front-man for a terror group's atrocities, and how he managed -- in spite at least five years of monitoring by security services -- to reach ISIS territory.

A U.S. intelligence source confirmed to CBS News on Thursday that "Jihadi John" is, in fact, Mohammed Emwazi. Now 27, Emwazi graduated in 2009 from the University of Westminster in London with a degree in computer science.

As CBS News' Mark Phillips reported Thursday, Emwazi had already garnered the attention of Britain's security services when he flew from London to Tanzania in the same year of his graduation from Westminster.

He was stopped upon arrival in east Africa by British and Tanzanian officials, who accused him of planning to go to Somalia to join the al-Shabaab militant group, which has since pledged allegiance to al Qaeda.

He said he was merely visiting for a safari vacation, but he was sent back to Europe on a flight to Amsterdam, where he faced more questions from intelligence agents before returning to London.

Britain's spy services continued to keep tabs on him as he lived with his family in a house in Queens Park, west London, until he disappeared in 2012.

Emwazi didn't reappear until ISIS released a video in August 2014, showing the execution of American journalist James Foley -- the first time the world saw "Jihadi John" wearing the now-familiar black hood and leather gun holster. He was given the nickname by a group of ISIS hostages, who dubbed their British captors "The Beatles."

Not long after the Foley execution, British and American intelligence agencies were confident they knew the real identity of the masked man, but they kept it quiet, presumably because they were trying to figure out who else he knew and how he ended up in ISIS territory.

Shiraz Maher, of the Center for the Study of Radicalization and Political Violence at King's College London, told CBS News that "Jihadi John" quickly became a powerful symbol for ISIS.

"He's become a huge character to the international community of what we call 'fanboys' and 'fangirls,'" said Maher, describing the thousands of young Muslims around the world who "sit around and support the Islamic State virtually."

To them, said Maher, the presumed murderer "is a celebrity."

Michael Weiss, a columnist for the Foreign Policy magazine and co-author of the recent book "ISIS: Inside the Army of Terror," also said that while Emwazi likely doesn't serve in a command role for ISIS, his value to the group is tremendous, "because of where he comes from and because of his pedigree and his background."

He said through Emwazi, ISIS is able to "telegraph to the West, to the United States, to England: 'we're already in your midst; don't you understand? Your depraved, corrupt, infidel society, your civilization -- so-called -- produces people who want to come join the Islamic State.'"

An organization which advocates on behalf of Muslims who find themselves on the wrong side of Britain's counterterror investigations, CAGE, has tracked Emwazi's encounters with intelligence and law enforcement agents for years.

Speaking Thursday at a news conference in London, Asim Qureshi of CAGE said Emwazi, who first contacted the group in 2009, "was extremely kind, extremely gentle, extremely soft-spoken, was the most humble young person that I knew."

Qureshi and his group suggested that years of harassment and unfounded snooping on Emwazi and his family eventually drove the Londoner to adopt an extremist mentality.

"When we treat people as if they are outsiders, they will inevitably feel like outsiders, and they will look for belonging elsewhere," said Qureshi.

But Weiss suggested that Emwazi fits perfectly into a familiar pattern of young Muslims in Europe who come not from deprived, under-educated backgrounds as some might expect, but relatively stable family environments.

Young men like the so-called "underwear bomber" Umar Farouk Abdulmutallab, who was sentenced to life in prison for trying to blow up a plane over Detroit on Christmas Day, 2009. Abdulmutallab, the son of a Nigerian diplomat, was radicalized during his college days in London, where he became a member of the student Islamic society at another prominent university.

"This is all too characteristic in Europe and, at least in my experience, particularly in London," said Weiss. Emwazi "was like, out of central casting. Nothing out of this surprised me."

Regardless of whether the British law enforcement agencies' actions helped foster Emwazi's radical views, they did fail to stop him traveling to Syria and becoming the suspected killer of not just Foley, but also American journalist Steven Sotloff, Britons David Haines and Alan Henning and U.S. aid worker Peter Kassig.

"It's difficult to track individuals," acknowledged Weiss. "But if you have somebody who you think, or maybe you already have credible proof, who is trying to go off and join a foreign terrorist organization, then he comes back to the U.K., then he goes to Kuwait, then he returns to the U.K., then he makes it over to Syria in 2012 in the midst of this roiling civil war... it sort of boggles the mind how this one slipped through the cracks."