Tonight we are gaining new insight into what is now believed to be a meticulously planned attack at the Westgate Mall in Nairobi, Kenya.
Based on intelligence, an official tells CNN it does not appear the attackers just walked into the mall.
Instead the attackers may have had access to the mall's blueprints, detailing personnel and emergency exits.
Investigators are also looking into whether the attackers rented a store in the mall and possibly stored their weapons inside the place before the attack, which killed at least 61 people and caused the mall to partially collapse.
The FBI is in Kenya and ready to start combing through that wreckage. The agency is just awaiitng permission to go into the mall where they'll look for DNA and other forensic evidence that will eventually make its way back to America's top secret bomb lab - a facility that is expected to play a huge role in determining who was behind this attack.
Our Barbara Starr gained exclusive access to the lab and is OutFront with this report.