"Tamerlan Tsarnaev, one of the brothers accused of carrying out the Boston Marathon terror attack, was in possession of right-wing American literature leading up to the bombings, a new BBC documentary says. Tsarnaev subscribed to publications "espousing white supremacy and government conspiracy theories" — specifically, that the September 11 terror attacks and the 1995 Oklahoma City bombing were both orchestrated by the U.S. government. Another article Tsarnaev apparently had in his possession was about "the rape of our gun rights." He also had "material about U.S. drones killing civilians, and about the plight of those still imprisoned in Guantanamo Bay." The 26-year-old was killed in a shootout in Watertown, Mass., on April 19. His brother, 19-year-old Dzhokhar Tsarnaev, later surrendered. He pleaded not guilty to federal terror charges. Three people were killed and more than 200 others wounded when two powerful homemade bombs exploded near the race's finish line on April 15. Friends of the Tsarnaev brothers told the BBC that Tamerlan, a fledgling boxer, turned against the country and became passionate about Islam. "He just didn't like America," one friend told the BBC. "He felt like America was just basically attacking all Middle Eastern countries ... trying to take their oil." Before Dzhokhar Tsarnaev was captured, he reportedly scrawled a note inside the winterized boat where he was hiding. It read: "We Muslims are one body. You hurt one you hurt us all." In April, the Washington Post reported that the brothers were "self-radicalized" and motivated to kill, in part, by the U.S. wars in Iraq and Afghanistan. That month, U.S. officials told the Associated Press that Tamerlan was an ardent reader of jihadist websites and extremist propaganda, suggesting the brothers were motivated by an anti-American, radical version of Islam. The BBC documentary underscores previous reports that Tamerlan was the mastermind behind the terror attack and that Dzhokhar was influenced his older brother. Dzhokhar "was intimidated [by Tamerlan], that would probably be the best word," a friend said. "He took him very seriously. He was an authority." Dzhokhar, the friends added, "smoked copious amounts of pot" and "rarely prayed." The BBC report, "The Brothers Who Bombed Boston," airs Monday."