Al Qaeda's third in command — Mustafa Abu al-Yazid — has reportedly been killed in a remote part of Pakistan. (See al-Yazid in an interview last year.) Here's a quick guide to what happened, and what al-Yazid's death could mean for the war on terror:

Who was Mustafa al-Yazid?
The Egyptian-born al-Yazid, also known as Saeed al-Masri, was al Qaeda's top commander in Afghanistan and a key plotter in the Sept. 11 terrorist strikes. As the group's "money man," he managed secret bank accounts used to finance attacks. Functionally, he was a primary link between the lower echelons of the terror network and its top two leaders, Osama bin Laden and Ayman al-Zawahri, both of whom remain at large.

How was al-Yazid killed?
Al-Yazid and his family were in a house that was struck by a missile fired by a U.S. Predator drone on May 22, a high-ranking Pakistani intelligence official told The New York Times. Al-Yazid's wife, three daughters, his granddaughter, and several other people were also killed. The attack occurred in a village 16 miles from Miranshah, the main town in North Waziristan, a border region where many Taliban and al Qaeda militants have established a haven since the invasion of Afghanistan.

Are we sure he's dead?
This isn't the first time al-Yazid's death has been reported. Pakistani military officials claimed in 2008 that al-Yazid had been killed in fighting along the Afghan border, but he later appeared in propaganda videos. But this time al Qaeda has confirmed his death, according to the Maryland-based SITE Intelligence Group, which monitors jihadist websites.

How big a setback is this for al Qaeda?
It's "a major blow to al Qaeda," says Bruce Hoffman, a Georgetown University terrorism expert, as quoted in The Wall Street Journal. Al-Yazid was one of the organization's founding members. An American intelligence official said al-Yazid, 55, had "a hand in everything from finances to operational planning." In the short term, that means his death could undermine al Qaeda's ability to coordinate cross-border attacks against American and allied forces in Afghanistan. But the CIA has killed many others who served as al Qaeda's No. 3, and the group has always managed to replace them and continue its war on the West.

Sources: New York Times, Wash. Post, Wall Street Journal, Telegraph