The following script is from "Morten Storm" which aired on Dec. 30, 2012. Lara Logan is the correspondent. Howard Rosenberg, producer.
Just over a year ago in Yemen, a U.S. drone operated by the CIA unleashed a Hellfire missile killing one of the most wanted terrorists in the world, Anwar Al Awlaki. The American-born cleric had been waging Holy War against his own country. Because he was a U.S. citizen, it was one of the most controversial drone strikes in the campaign against al Qaeda.
To this day, the question of how the CIA zeroed in on Awlaki in that distant desert land remains a mystery. Some of that will be answered tonight and you'll learn how an unlikely Danish spy named Morten Storm managed to get inside Awlaki's world and become one of his most trusted friends. And how, Storm says, he helped lead that fatal missile to its target.
[Anwar Al Awlaki: As you send us your bombs, we will send you ours.]
By the time of his death, Anwar Al Awlaki was at the top of the U.S. terrorist kill list. The Muslim cleric had become notorious for his fiery Internet sermons that incited attacks against America.
[Anwar Al Awlaki: Jihad against America is binding upon myself, just as it is binding on every other able Muslim.]
Awlaki had plotted with the underwear bomber, Umar Abdulmutallab, and he inspired Nidal Hasan's shooting rampage at Fort Hood, Texas, that left 13 dead. He had become the operational leader of al Qaeda in Yemen and was in the midst of planning more attacks. Morten Storm was one of the few people Awlaki trusted, what he didn't know was that Storm had become a double agent working for Danish intelligence and their partners, the CIA, who wanted Awlaki dead.
Morten Storm: At that moment now, Anwar needed to die by any means. He needed to be stopped. That was--
Lara Logan: Even though he was your friend?
Morten Storm: He was not my friend. He was a person I needed to get close to to stop his evil in him.
Lara Logan: How dangerous do you think he was?
Morten Storm: Very dangerous.
The two first met in Yemen in 2006 when Storm, a Muslim convert from Denmark, was as radical as Awlaki.
Lara Logan: What did you think of him, the first time you met him?
Morten Storm: Very kind person. You know, his character was-- how-- what do you call it? A joyful character.
Lara Logan: Did you two get on well from the beginning?
Morten Storm: From the very first minutes.
Lara Logan: And so you became friends?
Morten Storm: Yes. I liked him because of his views of jihad, because that was my views as well.
Storm's path to extremism began in prison when he converted to Islam at 21 -- a troubled kid with a violent past who had never found his place in the sleepy Danish town where he grew up.
Lara Logan: What would people have said about you at that time? How would they have described you?
Morten Storm: My reputation as a young teenager, I could punch very hard. I used to knock out a full-grown man with one punch. So, that's-- and I was known for that.