Image: Tamerlan Tsarnaev accepts the trophy for winning the 2010 New England Golden Gloves Championship in Lowell
Handout / Reuters

TODAY   |  May 04, 2013

New details emerge in death of Boston bombing suspect

As NBC News Chief Justice Correspondent Michael Isikoff reports, new details have emerged regarding the cause of death of Boston Marathon bombing suspect Tamerlan Tsarnaev. Meanwhile, Homeland Security officials are under fire after allowing one of Dzhokhar Tsarnaev's friends into the country without a visa.

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>> emerging about the cae of death of one of the accused bombers and federal authorities once again facing some tough questions surrounding the case. our national investigative correspondent michael isikoff is in our washington, d.c. bureau for us. michael, good morning.

>> reporter: lester, good morning. tamerlan tsarnaev, the alleged instigator of the bombings whose body is being prepared for burial died from gunshot wounds and blunt force trauma to the head. one of dzhokhar tsarnaev's friends were allowed into the country when he didn't have a valid visa. authorities searched neighborhoods near the university of massachusetts dartmouth campus on friday looking for evidence that tsarnaev may have tested explosives before the bombings as more evidence emerges about bungling prior to the attack. federal officials admit that one of the accused bomber's friends, azamat tazhayakov entered the country in january on an expired student visa . he's one of three students charged with conspireing to obstruct justice in the case. homeland officials say they failed to share information with their own airport inspectors that tazhayakov's visa was no longer valid.

>> this investigation now after the fact has really just begun.

>> reporter: a criminal complaint says that tsarnaev told his friends he knew how to make a bomb a month before the attack. the three friends recognized the resemblance to tsarnaev as the fbi released photos on april 18th . instead of calling police, they went to his dorm room and removed a backpack with fireworks and laptop computer according to the complaint.

>> if somebody tells you they know how to make bombs and a month later there's horrific bombings in the city and there are pictures put up by authorities as possible bombers, then you know.

>> reporter: tazhayakov's lawyer denies his client hid anything from the fbi.

>> he's created fully with the authorities and looks forward to the truth coming out in this case.

>> reporter: meanwhile, federal investigators are also asking more questions about tamerlan tsarnaev's widow. material from an al qaeda magazine was found on her computer. officials stress they don't know who downloaded that material on russell's computer and acknowledge it could have been done by her husband or someone else. russell's lawyer says she had no involvement in the bombing and was shocked when she learned of i it. lester?