Nightly News   |  April 23, 2013

Phone, email records suggest suspects acted alone

The two brothers accused of setting off bombs at the Boston Marathon are believed to have acted entirely on their own, using instructions for bomb making from an online magazine. NBC’s Pete Williams reports.

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This content comes from Closed Captioning that was broadcast along with this program.

>>> good evening. despite his wounds, the surviving bombing suspect in boston is now communicating with investigators and apparently he's telling them he and his older brother acted alone with no outside help. in the grim business of terrorism, that would make these two what are called self-radicalized jihadists, a polite term in this case for the surviving accused cold blooded murderer who thought nothing of depositing bombs meant to kill and injure innocent citizens including children. we learned other new details about this case today. pete williams continues to lead our coverage of the investigation. he's in our washington newsroom tonight. pete, good evening.

>> reporter: brian, good evening. investigators say they think they know the answer to who did the bombing, just the two brother, and the surviving suspect has provided an answer as to why. now the fbi is trying to determine whether there's evidence to back up his story. as dzhokhar tsarnaev lies under guard in a boston hospital now upgraded to fair condition, federal officials say he's told interrogators that he and his older brother came up with the marathon bomb plot entirely on their own because they believe the u.s. wars in iraq and afghanistan were an attack on islam. officials say he claims tin instructions for making a bomb came from al qaeda 's online magazine "inspire" which contains a formula similar to the one the fbi says was used to make the bombs in boston . an employee at a firework company says that record shows that tamerlan tsarnaev bought two dozen large fire works at a store in new hampshire in february.

>> a little disturbing that i had an interaction with him. he was just an everyday customer. i dealt with him the same as i would anybody else who comes off the street.

>> reporter: several online instructions including the one in inspire recommend using the contents of fireworks a as bomb component. 5,000 miles away fbi agents were in the russian province of dagestan to interview the parents of the suspects. their mother insists her sons could not be terrorists.

>> what happened is a terrible thing, but i know that my kids have nothing to do with this. i know it. i'm mother. i have -- you know, i know my kids. i know my kids. really my kids would never get involved into anything like that.

>> reporter: in massachusetts, police are working to trace whatever weapons were used in thursday night's shoot-out fland the killing of one policeman and the wounding of another. remarkably, despite all the gunfire when police encountered the men in watertown, several law enforcement officials say the brothers appear to have had only a single semiautomatic handgun . now being analyzed by massachusetts police. state authorities say they'll file charges of their own later this week for the killing of sean collier, the m.i.t. exam pus policeman that they say the tsarnaev brothers shot. members of congress say they want answers about whether the intelligence community should have done more to follow up on the older brother tamerlan, after the russians complained two years ago that he appeared to be growing more radicalized.

>> what about his electronic footprint, the suspect's cell phone they were trying to use to track him, the laptop they were anxious to look for inside his apartment?

>> reporter: right. they have all that. they do have his cell phone today and they're looking through that for evidence that others may have been working with them, but they say every day they look into this, they become more convinced or leaning more toward a conclusion that the two acted alone, brian.

>> pete williams , thanks, pete in our washington bureau tonight.