Usama bin Laden appeared to be reaching for a weapon before being shot by a team of U.S. commandos at his compound in Pakistan, a senior U.S. official told Fox News.

The detail was among many disclosed Tuesday that helps fill out the narrative of the events leading up to the 40-minute raid that ended with bin Laden's death.

White House Press Secretary Jay Carney on Tuesday said that bin Laden was unarmed when U.S. forces arrived.

Other details about bin Laden's compound suggest the Al Qaeda figurehead felt relatively secure in his surroundings. There were no guards on site, according to a senior U.S. official. And according to the official, bin Laden had a "treasure trove" of electronic material on site -- more than one would expect from a terror leader worried about getting caught.

He apparently had no interest in surrendering when the CIA-led Navy SEALs team arrived for their capture-or-kill mission, the result of years of intelligence gathering and special training. The team encountered resistance "throughout the operation," Carney said.

Carney said the raid started with one U.S. team working its way up from the first floor of the main building, where bin Laden's family and one other family lived. Another U.S. team cleared a separate building on the compound where yet another family had been living alongside bin Laden.

The first team killed two Al Qaeda couriers and a woman who got caught in the crossfire on the first floor of the main building, Carney said. The team found bin Laden and his family on the upper two floors.

According to one source, 10 people who were likely family members were in the room with bin Laden, including several young children, as well as one of his wives. Some of the children ran out of the room during the fighting. There was also a toddler in the residence.

Carney said bin Laden's wife "rushed" somebody from the U.S. team but was shot in the leg. He said bin Laden also resisted and was killed after that. After the completion of the mission, the team gathered evidence and took the body away from the scene.

That data and evidence are now being analyzed by CIA staff at the agency's Virginia headquarters. "The U.S. is moving quickly to exploit this information before the cockroaches scatter," a senior defense official said.

Though the data could prove vital in ongoing counterterror operations by U.S. military and intelligence, the circumstances surrounding bin Laden's hideaway continue to raise concerns about how he was able to live in relative luxury in Pakistan for so long.

Lawmakers are raising serious questions about whether Pakistani officials offered him a safe haven. But the Pakistanis are trying to show they remain committed to fighting the radical elements that continue to terrorize their cities.

The U.S. official said bin Laden's wife and children who were on site at the time of the raid are now in Pakistani custody. Other U.S. officials say that while Pakistan was not informed of the mission, the country was helpful in leading the U.S. to bin Laden.

It has become clear, though, that the critical element leading to the mission was a stream of intelligence that started in 2003, leading the U.S. to the courier who led them to bin Laden.

The CIA monitored the compound in Abbottabad, Pakistan by satellite in the months leading to the raid and noticed a man agents believe to have been bin Laden walking in the compound and never leaving its walls, a source said.

The senior U.S. official who spoke with Fox News said the nickname of the courier was Abu Ahmed Al Kuwaiti, or "Father of Ahmed -- the Kuwaiti."

At least one of the brothers had Pakistani citizenship, but he and his brother were from Kuwait and spoke Arabic.

According to a U.S. official, the U.S. first learned of the nickname in 2003. The information came out of the CIA's interrogation program, though officials insist it did not come from waterboarding.

The following year, a detainee said bin Laden trusted the courier to carry his messages. The claim was run by Khalid Sheikh Mohammed, key architect of the Sept. 11, 2001, terror attacks, and he downplayed the courier's importance, claiming he was retired and out of the business. Another detainee also claimed not to know him.

However, the strength of the denials was seen as a red flag by the CIA since other detainees were consistently claiming the courier had a close relationship with bin Laden.

Intelligence officials eventually traced the courier to northern Pakistan and later to the specific compound where it turned out bin Laden was hiding.

Fox News' Jennifer Griffin and Catherine Herridge contributed to this report.