Next, we turn now to news from the investigation of those bombs at the boston marathon, just three and a half ago. Were there clues that could have been pieced together before it happened? That... See More
Next, we turn now to news from the investigation of those bombs at the boston marathon, just three and a half ago. Were there clues that could have been pieced together before it happened? That question was asked today on capitol hill. Abc's senior justice correspondent, pierre thomas, reports in. Reporter: Five days before the attack on the boston marathon, state and federal authorities identified the finish line as an area of increased vulnerability. Especially to small-scale bombings. Police say they beefed up security, and the tragedy still happened. But on capitol hill today, there was a demand for answers, as to why signals may have been missed. My fear is that the boston bombers may have succeeded BECAUSE OUR SYSTEM ILED. Reporter: Tamerlantsarnaev, the suspected mast mastermind of the bombing was interviewed by the fbi after a tip by the russians. Local police say they never were told. When information is out there that affects the safety of my community, I need to know that. Reporter: And there were more concerns. Many who knew the suspects after the photos were released, never came forward. Reporter: Law enforcement officials say tamerlan, the older brother, had a beard when they interviewed him in 2011. In that year alone they interviewed 1,000 suspected radicals in the boston area. Sources say even the fbi agents who interviewed him, did not initially recognize him from the photos released from the bombing scene. Pierre thomas, abc news, washington.
This transcript has been automatically generated and may not be 100% accurate.