Nightly News | May 16, 2013
>>> there's news tonight on the boston marathon bombing investigation. specifically, a previously unreported message that one of the suspects left as authorities were closing in on him. tonight, it's providing clues to a possible motive in this case. our justice correspondent, pete williams , has details.
>> reporter: as dzhokhar tsarnaev lay wounded and bleeding in a boat stored in a watertown back yard, investigators say, he picked up a pen, perhaps believing he was dying, and wrote on the inside of the wall boat was which later riddled with bullet holes when police fired on it. law enforcement officials said he wrote using crowd language that the marathon bombings were in retaliation for the u.s. military operations in iraq and afghanistan which he said were attacks against muslims. and officials say he wrote he expected soon to be joining his older brother tamerlan as a martyr in paradise. according to investigators, he said much the same while he was questioned in the hospital during the weekend after his arrest. as for his older brother, who was the subject of a background assessment by the fbi in 2011 , fbi director robert muller responded today to complaint that the boston police chief was never told about that until after the bombings. muller said police in boston were part of a joint terrorism task force that had access to all the information the fbi gathered after the assessment of tamerlan tsarnaev was closed for lack of evidence.
>> others on the task force may have participated in some way or shape, but because it was closed, it was not of serious -- serious enough to be taken up to the leadership.
>> reporter: and investigators say they're still not certain where the bombs were assembled. officials say the fbi thoroughly searched tamerlan tsarnaev's apartment including swabbing the drains. while they say they found potential pieces of bomb components, they did not find what they considered signs of a bomb factory . investigators believe his widow, catherine russell , could tell them more than she has, though her lawyers say she has been cooperating. pete williams , nbc news, washington.