Transcript for Officials Believe Tsarnaev Brothers May Have Had Help
We're going to turn to the latest in the boston bombings investigation. The new video we told you about, dzhokhar tsarnaev teasing his niece. We're hearing his voice for the first time. Give me a kiss. Okay. No, give me a kiss. At that girl. Now get out. No. Brian ross is here with more information on whether the bomber acted alone. Good morning, brian. Reporter: From the beginning, a plot hard to come the grips with. This morning, it continues to be the case. The fbi is still tracking what it calls persons of interest in russia and here in the united states. The younger tsarnaev brother said they never tested the bombs before setting them off that day two weeks ago today. And many law enforcement officials and members of congress believe the two men, or at least the older one, had to have been well-trained in bomb making during his 6-month trip to russia last year. There are people in the united states that the fbi would like to have conrsations with. The unknown is the little over six months in russia. Clearly, that is where they went from the process of radicalization to pro-violence. The older brother? The older other, and to violence. Reporter: The older brother, tamerlan, was in russia in a time when a chechen terror group lost two key leaders about the same age. Including a canadian citizen who was a professional boxer before becoming part of a movement. A few days before he was killed by russian forces in july of last year, tamerlan returned from russia to boston. The fbi continues to have great interest in the mother of the two bombers, zubeidat. She denies her and her family have any connection to terrorism. Her phone calls were recorded by russian security forces while she discussed jihad allegedly with sher son. Overnight, the mystery man called misha e maernlgd from his home and said he did not have anything to do with encouraging tamerlan. He said, I was not tsarnaev's teacher. I never taught him anything. If I had been his teacher, i would have told him doing something like this is very, very wrong and against the precepts of our religion. Reporter: The report says misha said he has been interviewed by the fbi and called the fbi during the interview to make sure it was okay to talk to reporters. He's a person of interest but not that much interest apparently. So many questions. To the latest on t
This transcript has been automatically generated and may not be 100% accurate.