The older of two brothers who allegedly bombed the Boston Marathon earlier this year had "right wing extremist" literature including information about gun rights and white supremacy.

The BBC program Panorama spent months speaking to friends in attempt to uncover what might have radicalized Tamerlan Tsarnaev, who was killed by police following the bombing.

In a report published on Monday, the network said that it had learned that Tamerlan subscribed to publications that promoted white supremacy. Some articles that were in his possession asserted that the government was behind both the terrorist attacks of September 11, 2001 and the Oklahoma City bombing in 1995.

One piece of literature discussed "the rape of our gun rights," and a white supremacist document argued that "Hitler had a point." Other materials described how mass killers acted calmly while carrying out their crimes.

BBC also discovered articles about the how U.S. drone attacks kill civilians and the suffering of prisoners at Guantanamo Bay.

But people who attended mosque with Tamerlan in Cambridge said that he had only turned to Islam out of frustration after his boxing career and attempts at becoming a U.S. citizen failed.

"As far connecting with the Islamic community here, to actually praying, being involved, doing acts of charity….all of those were pretty much lacking," mosque spokesperson Nicole Mossalam explained.

"I would say he was just a Muslim of convenience," she added.

Watch this video from BBC, broadcast Aug. 5, 2013.