Why are Americans joining the Islamic State group?
However, the love story did not end well, and the young woman became depressed. She later met a man over Skype fighting alongside the Islamic State group in Syria.
Her new internet friend, reported to be a 32-year-old Tunisian IS fighter, convinced Shannon to travel to Syria and marry him. She bought a plane ticket from Denver, Colorado to Turkey, where she hoped to be smuggled across the border into Syria.
However, as soon as Shannon stepped foot in Denver International Airport on 8 April 2014, she was surrounded by FBI agents and charged with attempting to provide material support to a terrorist organisation.
Around six months later, authorities arrested 19-year-old Mohammed Hamzah Khan in Chicago's O'Hare International Airport, along with his younger brother and sister as they were headed to join IS.
US media had barely sunk their teeth into the story of the Chicago siblings when three teenage girls from Denver were stopped in Frankfurt, Germany, also on their way to join IS.
|The IS group provides angry teenagers with a sense of belonging and family that is similar to the sense provided to gang members
- JM Berger
Wanting to belong
JM Berger, an expert on jihadi groups, believes Americans join IS due to emotional problems and a sense of "not belonging".
"The IS group provides angry teenagers with a sense of belonging and family that is similar to the sense provided to gang members," said Berger.
"The IS projects images of camaraderie mixed with a sense of heroism that no longer exists. This appeals to teenagers who are angry about their situation in America," Berger told al-Araby al-Jadeed.
Berger said most of the individuals whose cases he has followed closely suffer from failed emotional relationships, family problems, feelings of inadequacy and not belonging - and that these are the problems the IS group exploits to win new followers.
According to the director of national intelligence, James Clapper, approximately 180 US citizens have tried to join the IS group in Syria over the past year.
There are approximately seven million Muslims in the US, 20 percent of them being second-generation immigrants, according to a 2007 Pew study.
Many Muslim youths who are second-generation immigrants suffer from identity issues to a certain extent, due to having to reconcile different and sometimes contradictory cultures and ideals.
"Most of the people who join the IS suffer from alienation," said Joe Novak, a psychology researcher.
"All humans want to belong to a group or society, or adopt a cause. When a teenager grows up and feels a deficit in this regard, he or she will adopt causes that reflect him or her."
Novak believes second-generation Muslim immigrants are more prone to radical ideas "because of their connection to their ancestors and their search for their history. Sometimes they are attracted by history, which is when they become easy targets for the IS."
|Around 45,000 Twitter accounts disseminate IS propaganda on a daily basis|
According to intelligence estimates, around 100 US citizens are currently fighting for IS, while dozens of others have attempted to travel to Syria to join, but were intercepted en route.
Berger, who is supervising a research project for the Brookings Institute on IS propaganda on social media, said they had discovered 45,000 Twitter accounts disseminating IS propaganda on a daily basis.
"This number includes the accounts that have been created and deactivated during the time it took to gather the research data," said Berger.
According to the former director of the National Counterterrorism Centre, Mathew Olsen, IS "has created a very advanced propaganda machine and has been able to recruit hundreds from around the world. Its propaganda techniques are unprecedented in the history of terrorist groups."
Meanwhile, IS and its supporters post approximately 90,000 tweets a day, containing videos and pictures of murders and other forms of violence, according to US media reports.
Social media companies are not doing enough to curb the torrent of IS propaganda published on their sites, despite their security measures and user regulations, say analysts.
Adventure and money
IS has captured a territory the size of the UK and has a roving army of fighters that is larger in number than the UAE army, according to a report published by the New York Times.
According to the report, a Syrian IS fighter receives $400 a month, a married fighter receives an extra $100 for every wife he has and an extra $50 for every child he has, in addition to having his accommodation and fuel expenses paid.
"We have made several mistakes that have unintentionally helped promote IS propaganda in the media. This has sparked the excitement of youths who aspire to have adventures and make money, which has enhanced the IS' recruitment ability," said Joshua Keating, an editor at Foreign Policy magazine.
"Youth destroyed by unemployment, oppression and a lack of prospects in the Islamic world - and identity issues, and the desire for adventure in the case of the US, are all reasons that push youths to join IS."