Investigators also want to know what Tamerlan was doing with a known militant recruiter in the region named Mansur Mukhamed Nidal with whom Tamerlan was repeatedly seen leaving a controversial mosque in Makhachkala, the capital of Dagestan. Nidal was also killed by Russian authorities while Tamerlan was in Russia.
But despite what authorities said was photographic evidence the Tsarnaev brothers were behind the Boston bombing and comments reportedly from the surviving brother about how they executed the plot, family friend Britney Smith told ABC News she's not convinced.
"I was always taught to believe what you see and... what I see is two people walking with book bags. I don't see them planting down explosives. I don't see book bags being dropped," Smith said, apparently referring to images widely circulated by the FBI that show the brothers with bags either near or heading in the direction of each of the bomb sites. "If he [Dzhokhar] gets convicted and I see proof of him doing it, then I will be in total shock. I would be in disbelief and disgust that he would do that."
The ABC News Investigative Team includes Rhonda Schwartz, Cindy Galli, Angela M. Hill, Megan Chuchmach, Matthew Mosk, Ned Berkowitz, Lee Ferran, Randy Kreider and Rym Momtaz.