Talking to reporters in Washington, John Brennan, the president's counter-terrorism adviser, said: "If we had the opportunity to take bin Laden alive, if he didn't present any threat, the individuals involved were prepared to do that … He was killed in that firefight. But we were certainly prepared for that possibility" -- that he could be captured.
However, he said, "We were not going to put our people at risk. ... He was engaged and he was killed but if we had the opportunity to take him alive we would have done that."
Bin Laden was killed in Pakistan by a Navy SEAL team Sunday night and later buried at sea.
Asked whether bin Laden could have been hiding in his elaborate compound in a Pakistani city without official Pakistani support, Brennan said, "I think it's inconceivable that bin Laden did not have have a support system that allowed him to remain in that country for a considerable amount of time."
But Brennan said he would not speculate on official involvement at this time.
Though he would not comment on the technology involved, Brennan said, "We were able to monitor [the operation] in a real-time basis. It was probably one of the most anxiety-filled times in the lives of the people gathered [in the White House] yesterday. The minutes seemed like days."
Four people besides bin Laden were killed in the compound, including one of bin Laden's sons and one of his wives who tried to act as a human shield, Brennan said,
He said there wasn't complete agreement among aides that the operation should go forward and U.S. President Barack Obama made the decision himself -- "One of the ... gutsiest calls of any president in recent memory."
The president's reaction to the success of the mission? "We got 'em," Brennan said, quoting the president.
Obama said Monday at a Medal of Honor ceremony for two soldiers: "I think we can all agree this is a good day for America. Our country has kept its commitment to see that justice is done. The world is safer; it is a better place because of the death of Osama bin Laden."
Brennan said bin Laden's burial at sea was ''done in strict conformance with Islamic precepts and practices. ... We early on made provisions for that type of burial" -- suggesting that the burial had been planned for months. He refused to go into details about where the burial took place but said it was done to bury bin Laden within the 24-hour window required by Islamic law.
U.S. officials earlier used DNA samples to identify the body taken from a Pakistani compound as bin Laden's.
Bin Laden's unnamed sister died from brain cancer at a Boston hospital several years ago, an ABC News report said, and her brain was confiscated by the FBI. Blood samples and tissue from the sister's brain were "matched" to samples taken from bin Laden before he was buried at sea.
The FBI put the word "deceased" on bin Laden's "Most Wanted" poster on its Web site.
The site said, "Well before the events of 9/11, bin Laden had openly declared war on the U.S. and was committed to killing innocents. His al-Qaida group was responsible for the 1998 bombings of the U.S. embassies in Dar es Salaam, Tanzania, and Nairobi, Kenya. The attacks killed more than 200 people. Bin Laden was indicted for his role in planning the attacks and added to the FBI's Ten Most Wanted Fugitives list. Intelligence agencies quickly learned the 9/11 attacks were carried out by bin Laden's terrorist organization, and in October 2001 his name was added to the U.S. Department of State's Most Wanted Terrorists List."
Obama said in a televised address late Sunday a "small team of Americans" acting with "extraordinary courage and capability" attacked a compound at Abbottabad, about 35 miles from Islamabad, killing the man behind the worst terror assault ever perpetrated on U.S. soil, the Sept. 11, 2001, attacks that left "gaping holes in our hearts" and are "seared into our national memory."
"After a firefight they killed Osama bin Laden and took custody of his body. No Americans were harmed," Obama said.
"Justice has been done," the president said.
Senior White House officials providing background characterized the operation as a "surgical raid by a small team" designed to minimize collateral damage and risk to non-combatants in the compound or the neighborhood.
ABC News reported the strike force attacking the compound between 1:30 and 2 a.m. Sunday consisted of 20-25 U.S. Navy SEALs under the command of the Joint Special Operations Command in cooperation with the CIA.
White House officials said there was a gunbattle in which bin Laden "did resist the assault force" before being killed. Sources told ABC standard procedure would be for the SEALs to "double tap" bin Laden -- shooting him twice in the head.
Two U.S. helicopters and one from Pakistan were involved in the raid.
One of the American helicopters was damaged during the operation and U.S. forces then destroyed it with explosives,
The Wall Street Journal reported a Pakistani official said a Pakistani chopper crashed after being struck by insurgent firing.
Pakistani officials said the strike was a joint U.S.-Pakistan operation, but American officials said only U.S. personnel were involved.
"We shared our intelligence on this bin Laden compound with no other country, including Pakistan," one official told reporters. "In fact, only a very small group of people inside our own government knew of this operation in advance."
Soon after the raid, U.S. officials contacted Pakistani leaders and "a number of our close allies and partners throughout the world," one background briefer said.
The president said the tip about bin Laden's whereabouts came last year but it took "many months to run this thread to ground" and enough intelligence was gathered to order the mission to kill the long-sought terrorist leader.
"From the time that we first recognized bin Laden as a threat, the CIA gathered leads on individuals in bin Laden's inner circle, including his personal couriers," one senior official briefing reporters said. "One courier in particular had our constant attention. Detainees gave us his nom de guerre or his nickname and identified him as both a protege of Khalid Sheik Mohammed, the mastermind of Sept. 11, and a trusted assistant of Abu Faraj al-Libbi, the former No. 3 of al-Qaida who was captured in 2005."
The break came in August when intelligence forces confirmed information about where the courier and his brother lived -- a compound in Abbottabad, an affluent area north of Islamabad.
"When we saw the compound where the brothers lived, we were shocked by what we saw -- an extraordinarily unique compound" sitting on a large plot of land in relative seclusion, one adviser said.
Bin Laden was living in a million-dollar house several times larger than others nearby but which had no telephones or televisions, the officials said. The house was designed with security in mind, with few entrances, walls more than 12 feet tall and windows placed high.
"Intelligence analysts concluded that this compound was custom built to hide someone of significance," one official said during the briefing.
Obama cautioned bin Laden's death doesn't end the war on terror.
"The death of bin Laden marks the most significant achievement to date in our nation's effort to defeat al-Qaida," the president said. "Yet his death does not mark the end of our effort. There's no doubt that al-Qaida will continue to pursue attacks against us. We must -- and we will -- remain vigilant at home and abroad."
Obama also attempted to mute any potential backlash against the United States by telling the world's Muslims they are not the United States' enemy.
"We must also reaffirm that the United States is not -- and never will be -- at war with Islam," he said. "I've made clear, just as President [George W.] Bush did shortly after 9/11, that our war is not against Islam. Bin Laden was not a Muslim leader; he was a mass murderer of Muslims. Indeed, al-Qaida has slaughtered scores of Muslims in many countries, including our own. So his demise should be welcomed by all who believe in peace and human dignity."
The news created jubilation across the United States.
A boisterous, flag-waving crowd outside the White House sang "God Bless America" and other patriotic songs. Fans at a New York Mets-Philadelphia Phillies baseball game in Philadelphia chanted "U-S-A, U-S-A" to the initial befuddlement of the players on the field.
"It's just a huge gathering of energy. I think for many it's just a huge sigh of relief," one man in the crowd that gathered at Ground Zero in New York told CNN.
George W. Bush, who was in office when al-Qaida terrorists operating at the behest of bin Laden crashed jetliners into New York's World Trade Center, the Pentagon, and a Pennsylvania field on Sept. 11, 2001, called Obama after hearing bin Laden was dead, CBS News reported.
"I congratulated him and the men and women of our military and intelligence community," Bush said in a statement.
"The fight against terror goes on but tonight the American people sent a message that no matter how long it takes, justice will be done," said Bush, who had vowed bin Laden would be taken dead or alive.
It took nearly 10 years as bin Laden hid among supporters, with the United States and its allies hunting him in Afghanistan and Pakistan.
In essence, bin Laden became a casualty of the war he launched against the United States two decades ago.
Bin Laden, the son of a Saudi Arabian construction magnate, inherited a fortune reported to be $25 million when his father died. He became a devout Muslim who joined the fight in Afghanistan during the Soviet occupation.