It was a decade-long search to bring justice to America's number one enemy and the Obama White House knew there was no room for mistakes.

After months of planning, and weeks of intensified meetings, the president and his most senior counter-terrorism aides gathered in the White House situation room Sunday to observe the operation to capture or kill Usama bin Laden as it unfolded.

"[W]e were able to monitor on a real-time basis the progress of the operation from its commencement to its time on target, to the extraction of the remains, and to then the egress off of the target," Obama's Homeland Security and Counter-terrorism Adviser John Brennan told the press at a White House briefing Monday.

Administration officials refused to detail exactly what they meant by that other than to say there were some sort of visuals and other information that allowed officials to keep track of the situation continually.

"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. The minutes passed like days."

Tension and silence filled the room.

Then, the pay-off.

Mission commanders uttered the phrase: "Geronimo E-KIA". "Geronimo" was the mission code name for Usama Bin Laden. "E" stands for "enemy." "KIA" is, of course, "killed in action".

Obama remained calm, sources say, even as those long-awaited words were spoken. There wasn't an "ah-ha" moment, Brennan says, when everyone realized spontaneously that the man killed was indeed bin Laden. The identification process was multi-faceted.

Then, as each piece came together, there was a growing sense of confidence that they'd gotten the right guy.

Finally, it became clear that the operation was a success and those carrying it out were safe.

President Obama's response said it all: "We got him."