Investigators are trying to determine if the bombing suspects acted alone. The bombs that exploded at the marathon were simple and similar to ones law enforcement officials come across on a regular basis.
Robert Siegel speaks with Peter Bergen, CNN's national security analyst and author of Manhunt: The Ten-Year Search for Bin Laden — from 9/11 to Abbottabad, about the alleged link between al-Qaida and Iran.
Footage from privately owned surveillance cameras along the Boston Marathon route gave the FBI early clues about the bombing suspects. But the proliferation of cameras in America's big cities raises some tricky questions about the balance between security and privacy.
Steve Inskeep talks with Karen Greenberg, Director of Fordham University's Center on National Security, about defining terrorism, what it means to call an act domestic versus international terrorism and the political ramifications.
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