Details continue to trickle out about the background of the Boston Marathon bombers, with evidence mounting that the two suspects may have subscribed to militant Islamic beliefs.

Last week, twin bombs ripped through the flesh of hundreds present at the Boston Marathon in the most deadly terror attacks on U.S. soil since the Sept. 11 attack on New York and Washington in 2001. Boston saw more than 200 wounded, and an 8-year-old boy and a student from China were counted among the three killed in the blasts.

In the days after the attack, a massive manhunt led to the capture of 19-year-old Dzhokar Tsarnaev, after his older brother, 26-year-old Tamerlan Tsarnaev, was killed in a shootout with police.

While it remains unknown whether the two had direct ties to al-Qaeda or other violent extremist groups, the Tsarnaev brothers, ethnic Chechens who immigrated to the U.S. more than a decade ago, may have been influenced by online radical Islamic propaganda.

In an NBC report published Tuesday, younger brother Dzhokar Tsarnaev told investigators he and his brother got instructions on building bombs from Inspire, an online magazine published by al-Qaeda.

The jihadist publication has in the past included instructions on constructing bombs using pressure cookers, the method authorities believe the suspects used in the deadly attack last week.

In a CNN interview released Wednesday, Ruslan Tsarni, the suspects' uncle, alleged that Tamerlan Tsarnaev had been influenced by an unknown friend who "took his brain," and earlier in the week told the network his older nephew had been "brainwashed" by extremist Islamic ideology.

Russian intelligence told the Federal Bureau of Investigation (FBI) in 2011 about information that Tamerlan Tsarnaev followed extremist Islam, but FBI found no evidence of terrorist activity after interviewing him for several times.

Senator Marco Rubio, who attended a Senate Intelligence Committee meeting on the bombing incident Tuesday, was quoted as saying that there are "increasing signals" that the brothers became "radicalized by Islamic fundamentalist terrorists, basically, using Internet sources."

Homegrown militant Islam has emerged in recent years amid intense U.S. pressure on al-Qaeda and its splinter groups worldwide, which led to the killing of terror mastermind Osama bin Laden and the decimation of the organization's core leadership.

Homegrown jihadists do not always have personal contact with trained terror operatives - although cases vary - and many take inspiration from websites such as Inspire.

Radicals often isolate themselves from their communities, becoming highly critical of mainstream mosques, most of which condemn violent militancy. Richard Barrett, director of the Qatar International Academy for Security Studies, told Xinhua that an individual's radicalization can stem from a complex array of issues.

"The road to radicalization is always a personal one, affected by many issues to do with identity, a sense of belonging, a sense of purpose and all the other factors that many people face as they develop their own political and moral template," said Barrett, former coordinator of the United Nations al-Qaeda/Taliban Monitoring Team.

But subscribing to radical ideology does not always end in violence.

"The vast, vast majority never come close to the border line between radicalism and violent extremism," he said. "But the continuum exists and an individual may well be pushed along it as he explores alternative sources of information and interpretation."

To cross the tipping point, most people need a personal intervention from someone they respect and who can offer them answers and a clear path, which appears to be the case with the younger of the two brothers, as he was influenced by his older sibling, Barrett said.