As investigators dig deeper into the pasts of Tamerlan and Jahar Tsarnaev, some of the most important information could come from those who knew them best.
Tamerlan Tsarnaev's widow, Katherine Russell, the elusive Misha, and even the two men from Kazakhstan who were detained last week on a visa violation may turn out to be key to the case.
Outfront tonight: Tim Clemente is a Former FBI agent in counterterrorism who worked the investigations into the African Embassy bombings, and the USS Cole. And Phil Mudd is a former CIA Deputy Director of Counterterrorism and FBI Senior Intelligence Adviser.
After nearly a year of tough economic sanctions on Iran - sanctions that the U.S. says is having a "significant" impact on the country - there's no indication Tehran is bowing to the pressure.
Erin Burnett spoke to Seyed Shamseddin Hosseini, Iran's economic affairs and finance minister, and asked him about the effect of the sanctions on Iran.
As investigators dig deeper into what motivated the two brothers suspected of bombing the Boston Marathon, the city's Muslim community is also trying to figure out why Tamerlan Tsarnaev, a man they knew drifted toward radical Islam.
It is a question Muslim communities in America know all to well. Having been down this same path after 9/11 and the Fort Hood shootings.
OutFront tonight two men who have written on this very topic - Dean Obeidallah, a former practicing attorney and a political comedian
and CNN Contributor Reihan Salam.
According to Russia's state news agency, Russian security services have arrested and detained 140 people in the southern part of the Moscow region during an operation to crack down on individuals connected to Islamic extremist organizations.
There is no indication yet whether the arrests have any connection to the Boston bombings, but we do know that the arrests occurred at a place of prayer, named Dar Ul-Arkam - a place that known radicals have visited, including those who have taken part in preparing and carrying out extremist actions in Russia.
OutFront tonight: Republican Congressman Ed Royce – Chairman of the House Foreign Affairs Committee.