The Washington Post reported that the CIA had a safe house in Abbottabad for its spies to operate.
They recruited Pakistani informants to report on activities around the compound.
The massive surveillance effort included satellites and sensitive microphones to pick up voices inside the compound.
U.S. officials said they believe bin Laden went to Abbottabad to escape a possible attack by CIA drones in the northern tribal areas, but it proved to be his biggest mistake.
As more details are released about the raid, they contradict what was originally told by the White House.
The two dozen Navy SEALs involved in the operation returned to the U.S. and were debriefed about exactly what happened inside. It turns out the firefight inside was one sided, and the only person to fire at the SEALs was a courier on the first floor.
As the mission continued upstairs, no one else fired a gun except the SEALs. However, there were several guns found inside the compound. The military defended the decision of the SEALs to fire, insisting that it was a dangerous situation and the SEALs simply surprised them.
"I don't understand the implication: SEALs 'only' fired upon once,'" said one U.S. official. "How many times do you have to be shot at by bin Laden's henchmen before it's reasonable to fight back? These guys are American heroes. They were told to kill bin Laden. We've had the authority to kill bin Laden since Sept. 11, and that's exactly what they did."
When Secretary of State Hillary Clinton was asked whether shooting bin Laden was a mistake, she said bin Laden had been a clear target for U.S. and allies for 10 years.
"No question his death will make the world safer and empower builders, not destroyers," she said.
Mistrust between Pakistan, U.S.
When the helicopters lifted off with bin Laden's body, his 29-year-old wife, who had been shot in the leg trying to protect him, was left behind.
She is now talking to Pakistani investigators, but they won't let the U.S. talk to her. A senior Pakistani official said there is "complete mistrust" between the two countries.
"How could bin Laden have gone undetected living next door to Pakistan's equivalent of West Point?" said Sen. John Kerry.
The U.S. has given $20 billion to Pakistan for counterterrorism efforts since the Sept. 11 attacks. It is unclear if that funding will continue.
"They're either supremely incompetent or supremely duplicitous. Neither one is a good place to be in," said Sen. Chuck Schumer.
Pakistan is warning the U.S. against any more missions like the raid on bin Laden's compound. Pakistani Foreign Secretary Salman Bashir said there will be "disastrous consequences" if any more unauthorized raids are carried out against terrorist suspects.
"It's easy to say that the Inter-Services Intelligence or elements within the government were in cahoots with the al Qaeda. This is a false hypothesis," Bashir said.
Bashir questioned whether the U.S. raid complied with international law, based on a violation of Pakistani sovereignty.
"The violation of sovereignty raises legal issues that fall in the domain of U.N.," said Bashir. "There are legal questions based on the principles of the U.N. charter and several Security Council resolutions."
Pakistani leaders said that they were not aware of the raid until it was too late to stop it. But Bashir wouldn't go so far as to say the mission was actually illegal, and insisted that relations between the U.S. and Pakistan are stable.
Considered an expert on terrorism from her nine terms in Congress and the House Intelligence Committee, Jane Harman said she's convinced the U.S. needs Pakistan's help in the war on terror.
"If we are not friendly with Pakistan and working on the same team, I think we could lose ground in this era of terror," she said. "Terror does not go away because Osama bin Laden was killed."
Info from raid reveals plan to attack trains
Some of the first information gleaned from bin Laden's compound indicates al Qaeda considered attacking U.S. trains on Sept. 11, but U.S. officials say they have no recent intelligence indicating such a plot is active.
A Homeland Security intelligence warning sent to law enforcement officials around the country says that as of February 2010, the terror organization was considering tampering with an unspecified U.S. rail track so that a train would fall off the track at a valley or a bridge.
This information appears to be the first widely circulated intelligence pulled from the May 1 raid on bin Laden's secret compound.
After killing bin Laden, Navy SEALs took computers, DVDs and documents from his house.
Officials said some of the material is not actionable, but nonetheless valuable in terms of assessing risks in different regions.
The Associated Press contributed to this report.
