Agonizing "minutes passed like days," after Barack Obama made what a top aide dubbed the "gutsiest" presidential call in years, and followed in real time as special forces swooped on Osama bin Laden.
Obama's gruff anti-terror advisor John Brennan, who hunted the Al-Qaeda mastermind for 15 years, offered tantalizing details Monday of the high-stakes operation in the Pakistani city of Abbottabad in which bin Laden died.
"It was probably one of the most anxiety-filled periods of time, I think, in the lives of the people who were assembled here yesterday," Brennan told reporters in a colorful White House briefing.
"The minutes passed like days, and the president was very concerned about the security of our personnel."
Brennan would not say exactly how Obama and his top advisers were able to follow Sunday's 40-minute Navy SEAL operation unfolding in real time in the White House Situation Room.
But the suspicion was that some kind of sophisticated communications technology was available to them, possibly with video or photographs transmitted back from the scene.
"It was clearly very tense, a lot of people holding their breath," Brennan said. "And there was a fair degree of silence as it progressed as we would get the updates.
"When we finally were informed that those individuals who were able to go in that compound and found an individual that they believed was bin Laden, there was a tremendous sigh of relief."
Brennan was also asked several times whether the national security team had been able to hear exchanges of fire in the compound where bin Laden was sheltering but demurred.
"We were able to monitor the situation in real time," was all he would say.
The White House later released a photo of Obama and key aides watching action unfold on the operation, apparently on a screen that is out of shot in the White House Situation Room.
Obama is seen sitting to one side, staring intently at the screen. Secretary of State Hillary Clinton has a hand over her mouth, while other officials look on with deep concern etched on their faces.
"I can say that was during the period of time that the team was on the target," a senior official said on condition of anonymity.
Had the sophisticated helicopter-borne operation gone wrong, the stakes for Obama would have been huge, and the operation could have dealt him a political blow from which he would not recover as he seeks reelection next year.
Given the downside risk, Obama faced the kind of lonely decision that only the presidents who have made such perilous calls before can understand.
"The president had to evaluate the strength of that information and then made what I believe was one of the most gutsiest calls of any president in recent memory," Brennan, a former senior CIA officer, said.
Brennan said the most anxious moment of the operation came when one of the helicopters carrying Navy SEALs special forces developed technical problems after flying into the compound.
"When that helicopter was seen to be unable to move, all of a sudden, you had to go into Plan B. And they did it flawlessly," said Brennan, describing the moment when another helicopter was called into the breach.
Another senior US official confided on condition of anonymity that the other key phases of the operation came when the officials back in the Situation Room were told that Bin Laden was indeed in the compound.
In the next update, the team was told that the US nemesis had been shot dead.
The exact circumstances of bin Laden's final moments remained unclear. One official confirmed that the Al-Qaeda leader was shot in the head, and some reports also suggested he took a round to the chest.
"It was very quiet, you are sitting there in silence waiting for the next information. The president was very stoic."
When Obama learned bin Laden was dead, he said "we got him guys" but told aides that he wanted to be informed immediately the helicopters landed back at base -- the location of which US officials have not disclosed.
Brennan also revealed that the United States did not inform the Pakistanis about the operation until its helicopters had exited Pakistani air space, and of fears that Islamabad would scramble fighters to intercept the mission.
US authorities weighed the idea of some kind of direct missile strike; a commando raid similar to what was launched; and waiting longer to assess the situation at the home, said a senior US official on condition of anonymity.
Obama always had been determined, from his time on the campaign trail, to step up the long hunt for bin Laden, the official added.
In the end, the US president made his call based on his confidence in the commanders being able to carry out the job, the US official added.
US forces on the scene carried out facial identification of the Al-Qaeda leader with special techniques.
The CIA gave them a 95 percent assurance that it was bin Laden, the US official said, noting that they also identified him through his unusual height and the fact that they asked other people in the compound if it was he.