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al-Qaeda's new leader - Ayman Al-Zawahiri

The death of al-Qaeda's leader leaves control of the terrorist organization in the hands of Osama Bin Laden's number two - Ayman Al-Zawahiri.

Reporting on TODAY this morning, NBC's Chief Foreign Correspondent Richard Engel told Matt Lauer, "Perhaps because of Al-Zawahiri's medical background, Matt, Ayman Al-Zawahiri has long expressed a keen interest in chemical and biological weapons."

Watch Richard's report above.