(CNN) -- Abu Yahya al-Libi, al Qaeda's No. 2 man, was killed in Pakistan on Monday, according to U.S. officials.

Al-Libi's death was "another serious blow to core al Qaeda," White House spokesman Jay Carney said.

Al-Libi, 49, was a well-regarded figure in jihadist circles and had emerged as one of the terrorist network's most important clerics and propagandists, appearing in countless videos in recent years.

He was killed by a CIA drone strike, according to U.S. officials. Drone strikes remain a highly contentious issue between the United States and Pakistan.

Who is Abu Yahya al-Libi?

By most accounts, al-Libi was effectively al Qaeda's deputy leader.

A Libyan citizen and an Islamic scholar, al-Libi bolstered his credibility within jihad groups after escaping from U.S. custody in Afghanistan in 2005.

He became the public face of al Qaeda and used his religious training to justify the organization's actions. As one of the group's chief ideologues and propagandists, al-Libi appeared in numerous recruitment videos in which he cast himself as a sheikh with the legitimacy to issue fatwas.

Other than his appearances in propaganda videos, it's unclear which plots against the West al-Libi was involved in. A wanted ad from the U.S. State Department described him as a "key motivator in the global jihadi movement," and said that "his messages convey a clear threat to U.S. persons or property worldwide."

What does his death mean for al Qaeda?

This is a "very serious blow" to al Qaeda, according to Noman Benotman, a former senior member of the Libyan Islamic Fighting Group who spent significant time with al-Libi in the 1990s. No one else within the group rivals his legitimacy as a religious scholar nor has the credibility in the Arab world to provide Islamic justifications for al Qaeda's global campaign of terrorism, he said.

1. WHO WAS KILLED?
2. WHERE?
3. WHAT DAY?
4. WHAT RADICAL GROUP WAS HE A PART OF?
5. HOW OLD WAS HE?
6. WHAT CIRCLE WAS HE A WELL REGARDED FIGURE OF?
7. HOW WAS HE KILLED?
8. WHO IS GIVING THIS INFORMATION?
9. BETWEEN WHAT TWO COUNTRIES DO DRONE STRIKES REMAIN A HIGHLY CONTENTIOUS ISSUE?
10. WHAT DID AL-LIBI DO FOR AL QAEDA/
11. WHERE WAS HE A CITIZEN FROM?
12. WHERE DID HE ESCAPE FROM IN 2005?
13. WHAT DID HE USE TO JUSTIFY ORGANIZATION'S ACTIONS?
14. WHAT TYPE OF VIDEOS DID HE OFTEN APPEAR IN?
15. HOW DID A WANTED AD FROM THE US STATE DEPARTMENT DESCRIBE HIM AS?
16. HOW DID THE US CONSIDER HIS MESSAGES?
17. WHAT DOES HIS DEATH MEAN FOR AL QAEDA?
18. WHO SAID THAT?
19. WHO IS HE?
20. DID HE KNOW HIM PERSONALLY?
21. HOW DID THEY KNOW EACH OTHER?
22. WHAT YEAR DID THAT HAPPEN?
23. WHO IS SPOKESMAN OF WHITE HOUSE THAT TALKED ABOUT AL LIBI?
24. WHAT TYPE OF SCHOLAR WAS AL LIBI?
25. WHAT WOULD AL LIBI CAST HIMSELF AS IN HIS VIDEOS?
26. WHAT PLOTS IN THE WEST WERE BEING WORKED ON BY HIM?
27. WHAT POSITION DID HE HAVE IN THE AL QAEDA?
1. Abu Yahya al-Libi
2. Pakistan
3. Monday
4. al Qaeda's
5. 49
6. jihadist circles
7. CIA drone strike
8. U.S. officials
9. United States and Pakistan
10. al Qaeda's deputy leader
11. Libyan citizen
12. U.S. custody in Afghanistan
13. religious training
14. ecruitment videos
15. "key motivator in the global jihadi movement,
16. a clear threat
17. very serious blow" to al Qaeda
18. Noman Benotman
19. former senior member of the Libyan Islamic Fighting Group
20. YES
21. spent significant time with al-Libi
22. 1990s
23. Jay Carney
24. Islamic scholar
25. sheikh with the legitimacy to issue fatwas
26. it's unclear
27. al Qaeda's No. 2 man