Anchored by Jake Tapper, The Lead airs at 4 p.m. ET on CNN.
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The question of whether the accused bombers had collaborators has yet to be definitively answered. The surviving brother, Dzhokhar Tsarnaev, has told investigators they acted alone, according to law enforcement sources, telling investigators he and his brother were inspired by what they saw as unjust wars in Iraq and Afghanistan, and radicalized themselves by what they read online.
The preachings of radical American cleric Anwar al-Awlaki were likely to have been among the videos the Tsarnaev brothers watched, according to a U.S. government official.
Investigators are also looking into whether the brothers read the jihadist online magazine "Inspire," the brainchild of al-Awlaki, the magazine reads like a how-to manual for would-be terrorists.
"For a number of years, that one magazine seemed to be a main recruiter of young Muslims in this country in terms of self-radicalization," Rep. Peter King, R-New York, said shortly after the Boston bombings.
One of the pressure cooker bombs allegedly used by the Tsarnaevs was similar to a bomb design found in the magazine's article "How to Make a Bomb in Your Mom's Kitchen."
Tamerlan Tsarnaev also has an online footprint. After his trip to Dagestan and parts of Russia, including Chechnya last year, it appears Tamerlan created a YouTube channel on which he posted and then removed a video of a jihadist leader who was later killed by Russian troops.
"If you go back to the early '90s, Europeans went to Chechnya to fight. They came back to Europe and became terrorists in Europe. We saw that in France and other parts of Western Europe," said Michael Chertoff, former Secretary of Homeland Security. "So there is a history of people going to the region and coming back radicalized."
Radical philosophies are appealing to certain kinds of people, says Daniel Lieberman, professor of psychiatry and behavioral sciences at George Washington University.
"They can give very easy answers to difficult questions, such as for people who are misfits, 'What's wrong with me? Why do I feel like such an outsider?' And these are the kinds of answers that can be found on radical sites on the internet," said Lieberman.
The idea that internet videos could take someone, like the Tsarnaev brothers, and turn them into something they were not already is difficult for many to believe.
"Radicalization does involve social involvement. But that's what social media is," said Lieberman. "We don't know how exactly it compares to direct social interaction, but it seems to have a lot of the same influence."
Lee Smith argues in Tablet Magazine that there is no "self" in "self-radicalization," that there is an apparatus. Smith wrote on Thursday, "These attacks are not accidents of individual psychology or humiliation. They are part of a larger plan shaped by some very smart sociopaths to use such people for horrific ends."
"We know the intense kind of influence social media can have on people, we know of people falling in love on Facebook, leaving their families to pursue this virtual relationship," said Lieberman. "It can lead people to behave in ways that ordinarily they would not consider."
Adding in the fact that jihadi plays a role, makes for an even more intense situation. Lieberman says the religious element, the idea of self-radicalization becomes much more problematic.
"When people think of acting in their own self-interest, death takes on a very different meaning," said Lieberman. "In secular terms, death is something to be avoided. If you think you're going to be rewarded and go to paradise, then it becomes very different."