The attacks in Paris and California have many wondering how seemingly ordinary people, many from prosperous Western countries, become radicalized.
The son of a Moroccan-born market vendor and his Belgian-born civil servant wife dropped out of high school his senior year and later began to study sports therapy.
[...] he became outraged over the deaths and suffering of Palestinians in Gaza and the atrocities of Syria's civil war.
FBI agents became aware of her interest in jihad after she discussed it with members of her suburban Denver church, and they arrested her in April 2014 as she boarded a plane on her way to Syria.
The 21-year-old Muslim convert took an interest in Syria, mainly through online militant videos, while serving a prison sentence for assault and robbery.
In September 2014, he was arrested with three others in Germany on charges of assaulting a 52-year-old man of Egyptian origin outside his home, forcing him into a car and demanding 100,000 euros from the family for his release.
Authorities found extremist materials on Dzhokhar's computer and other electronic devices, including an issue of the al-Qaida magazine Inspire and audio lectures by Anwar al-Awlaki, an American-born al-Qaida ideologue killed in a U.S. drone strike in Yemen in 2011.
[...] in his early 20s, Uka became increasingly introverted, spending most of his time at home playing computer games and watching radical Islamic propaganda on the Internet.
In March 2011, at age 21, he watched a video posted on Facebook that purported to show American soldiers raping a teenage Muslim girl.
After confirming that a bus was carrying U.S. Air Force members bound for Afghanistan, he shot one airman in the head, killing him, and then boarded the vehicle, shouting "Allahu Akbar!" ("God is greatest!") and killing the driver.
[...] as a government siege tightened around the Old City section of Homs, he grew closer to hard-line Islamic militants, including fighters from an al-Qaida affiliate.
[...] at 19, while studying radiography in her hometown of Glasgow, Scotland, she abruptly left in November 2013 and traveled to Syria to join the Islamic State group, authorities say.
[...] she has been accused of using social media to recruit other girls to follow in her footsteps.
Authorities believe she is a key figure in a female brigade charged with enforcing the IS group's harsh interpretation of Islamic law.
