The Pulse: Hero again: Immigration agent Jose Melendez-Perez helped to foil bin Laden not just once, but twice.

An amazing story just became more so.

Many, including me, already credit Jose Melendez-Perez with preventing a direct strike on the nation's capital on Sept. 11, 2001. Now a case can be made that he played a key, albeit indirect, role in the killing of Osama bin Laden.

On Aug. 4, 2001, Melendez-Perez was working as an immigration inspector at Orlando International Airport. He was the secondary screener that day, the one people are sent to when "something is not right," Melendez-Perez told me in 2005. When a Saudi national named Mohammed al-Qahtani arrived from London, he was sent to Melendez-Perez.

The veteran immigrations inspector continued: "In this particular case, the person was referred because he didn't have his I-94 - which is a traveling document - properly completed, because he claimed he didn't speak any English. Well, I thought there was something wrong with the individual based on the way he looked at me when I went to get him out of the waiting room. This guy had this very deep stare. . . . I never saw that before.

"A traveler coming to the United States referred to secondary normally will behave in a normal manner. But this guy's body language and the way he looked at me told me that something wasn't right. The guy was challenging me for some reason. I thought that the guy was upset about something. He gave me this look that says, 'I can take you down anytime,' something like that. At about three occasions I got up from my chair and went outside because I had this cool chill sensation through my body."

Melendez-Perez wasn't thinking bin Laden or al-Qaeda. A month before 9/11, he didn't know about either of them. He simply trusted his instincts, which were telling him that he had a man up to no good in front of him.

Against the counsel of colleagues concerned about the political clout of Saudi nationals, Melendez-Perez turned the visitor around and sent him back.

Four months later, Qahtani was captured in the Tora Bora region of Afghanistan after fighting coalition forces on behalf of bin Laden, whom he had seen just days before. Because Qahtani's data were in computers as a result of Melendez-Perez's interrogation in Orlando, the Saudi triggered further inquiry that eventually enabled the 9/11 Commission to recognize his intended role in the attacks.

Mohamed Atta, the 9/11 ringleader, was at Orlando International on Aug. 4 to pick up Qahtani. But for Melendez-Perez's intervention, Qahtani would have been the fifth terrorist aboard United Flight 93 - the 20th hijacker. That is why 9/11 commissioners John Lehman and Richard Ben-Veniste have recognized his role.

"Customs Officer Jose Melendez-Perez stopped the 20th terrorist, who was supposed to be on Flight 93 that crashed in Pennsylvania. Probably because of the shorthanded muscle on that team, the passengers were able to overcome the terrorists," Lehman said in 2004.

Ben-Veniste has told me he regards Melendez-Perez as a "true American hero." He continued: "But for his actions . . . the Capitol building might have been destroyed on 9/11."

As I said, it's an amazing story, and now there's more.

Accounts last week by NBC investigative reporter Michael Isikoff and others indicate that Qahtani was one of the Gitmo detainees - perhaps the first - to describe the trusted courier that ultimately led U.S. investigators to bin Laden's compound in Abbottabad. That courier, who was among those killed trying to protect bin Laden last Sunday, reportedly provided computer and Internet training - at Khalid Sheikh Mohammed's request - to Qahtani before he traveled to Orlando.

Meanwhile, a Wikileaks-released government file on Qahtani reveals how he swore bayat - a loyalty oath - to bin Laden, who personally selected the young Saudi for a "special mission." The document also details a post-9/11 speech bin Laden delivered to Qahtani and others: "Approximately 25 November 2001, detainee saw UBL in Tora Bora giving a speech to the leaders and other fighters. UBL told them to remain strong in their commitment to fight . . . and that it was a grave mistake and taboo to leave before the fight was completed."

On Dec. 5, 2001, Qahtani was praying in a cave in Tora Bora with other fighters when bin Laden appeared and prayed with the group. Ten days later, Qahtani was captured. In February, he was shipped to Guantanamo Bay, where he provided one of the bread crumbs that led to bin Laden.

U.S. forces were able to follow those crumbs all the way to Abbottabad because, before anybody else got to Qahtani, Melendez-Perez prevented the intended 20th hijacker from entering the United States and fulfilling his deadly mission aboard Flight 93.