One senior U.S. official speaking on condition of anonymity told NBC News that Saeed was killed in an attack by a missile-carrying drone aircraft.
Another official said that "in terms of counterterrorism this would be a big victory," describing Saeed as "the group's chief operating officer, with a hand in everything from finances to operational planning. He was also the organization's prime conduit to Osama bin Laden and Ayman al-Zawahiri. He was key to al-Qaida's command and control."
In a series of interviews with Al Jazeera last year, al-Yazid swore that Pakistani nuclear weapons would be used against the US and allied countries if they obtained access to them. (See video above)
More information here about Al-Yazid and his involvement in terrorist training and Afghanistan.