(NBC News) A preliminary examination of the cellphones and computers used by the Tsarnaev brothers has found no indication of an accomplice in the Boston Marathon bombing, according to a U.S. counter-terrorism source briefed on the FBI investigation.
The source stressed that the investigation is ongoing, but bureau officials at this point appear increasingly confident that “nobody else was involved,” said the source.
Dzhokhar Tsarnaev has told investigators he and his brother acted alone, learned to build the pressure-cooker bombs over the Internet and were motivated by a desire to defend Islam because of "the U.S. wars in Iraq and Afghanistan," said the source, who has received multiple briefings on the probe.
Dzhokhar Tsarnaev has also told investigators that he and his brother got instructions on building bombs from an online magazine published by al Qaeda, federal law enforcement officials told NBC News.
He told investigators that the brothers read the instructions in Inspire, an online, English-language magazine that terror monitoring groups say al Qaeda began publishing in 2010.
The magazine has twice included articles on building bombs with kitchen pressure cookers — the method investigators say Tsarnaev and his brother, Tamerlan, used in the Boston attack.
Read the entire report from NBC News HERE.