A nearly decade-long manhunt for the mastermind of the worst terrorist attacks on U.S. soil ended north of Pakistan's capital Monday as American commandos killed al Qaeda leader Osama bin Laden in a pre-dawn firefight. The raid on bin Laden's compound in Abbottabad, about 50 kilometers (31 miles) north of Islamabad, came about four years after U.S. intelligence officials identified a man who served as one of the al Qaeda leader's trusted couriers, according to senior Obama administration officials. Bin Laden was shot in the head and chest during the operation, a senior administration official told CNN. White House counterterrorism adviser John Brennan said that despite intelligence indicating that he was in the compound, there was no certainty the al Qaeda leader was actually there when the president authorized the assault. "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 Monday afternoon. "The minutes passed like days, and the president was very concerned about the security of our personnel. "When we finally were informed that those individuals who were able to go on that compound had found an individual that they believed was bin Laden, there was a tremendous sigh of relief that what we believed and who we believed was in that compound actually was in that compound and was found. And the president was relieved once we had our people and those remains off-target." The president and top aides were gathered in the White House situation room to monitor the progress of the operation Sunday afternoon when the message "Geronimo EKIA" -- indicating that bin Laden had been killed in action -- was called in from Pakistan. The operation recovered "quite a bit of material" that intelligence officers will be sifting through to track down other al Qaeda figures, a senior U.S. intelligence official said. Brennan called the decision "one of the most gutsiest calls of