But the agent, who asked not to be identified discussing Paddock, said they never knew Paddock to be political or ideological. A person familiar with the investigation into the massacre said these anti-government views alone didn't explain why Paddock would head to a 32nd floor suite at the Mandalay Bay Resort and Casino, break out the windows and open fire into a crowd of unsuspecting citizens.
This much is certain: Paddock, 64, aimed for maximum destruction. He had with him in the suite 23 guns, a dozen of them equipped with bump stocks that would allow for rapid fire, along with thousands of rounds of ammunition that he never fired.
These bump stocks have become a flash point since the shooting, and on Thursday the National Rifle Association - in its first statement since the massacre - echoed others in calling for more regulations on the devices.
Investigators searching Paddock's car also found several cases containing the chemical tannerite, an explosive, and 1,600 more rounds of ammo.
But Paddock, who killed himself before police stormed his suite, left precious few clues about his motive. There was a slip of paper in his suite, authorities said, but it was not a suicide note. As of Thursday afternoon, the only new information to publicly emerge from searches of Paddock's electronic equipment were details of his possible travel plans.
He had booked space at the Blackstone Hotel near Chicago's Lollapalooza in August, and the following month, reserved a room at the Ogden in Las Vegas during the Life is Beautiful festival.
It seems he never actually checked into the Chicago hotel, though an official said investigators were still exploring his travels. They were also looking at possible interest Paddock had in Boston, an official familiar with the case said.
Paddock, a retired accountant and avid gambler, was "disturbed and dangerous," Joseph Lombardo, the Las Vegas sheriff, said at a news briefing Wednesday night.
"Stephen Paddock is a man who spent decades acquiring weapons and ammo and living a secret life, much of which will never be fully understood," Lombardo said.
Authorities have said that Paddock had ramped up his gun purchases in the year before the shooting, and Lombardo said police were trying to determine whether something in his life changed during that period.
"Anything that would indicate this individual's trigger point and would cause him to do such harm, we haven't understood it yet," he said.
The emerging portrait of Paddock suggested a man of considerable means who liked guns, gambling and women, but who so disliked interacting with people that he sought to avoid talking to them.
Property records show Paddock sold several low-end apartment buildings and commercial buildings in California in the 2000s before purchasing an apartment building in Texas and homes in retirement communities in Florida and Nevada. Between 2003 and 2004, Paddock sold at least three commercial properties in California for a total of more than $5 million dollars.
Paddock would buy apartments, move into them to keep an eye on his investment, but "still would employ other people to talk to the tenants because he didn't want to talk to the tenants," the broker said.
The aversion to human interaction even extended into Paddock's flying, said the broker, who like Paddock enjoyed piloting personal planes.
At the time of their acquaintance, Paddock had a sleek new aircraft - a Cirrus SR20. On the handful of flights they made together Paddock would refuse to respond to air traffic controllers and mapped out his path - steering away from controlled areas - just to avoid having to talk to them, the broker said.
Paddock stored the Cirrus at a Mesquite Metro Airport hangar between 2007 and 2009, according airport workers. The airport staff had little recollection of him, said Lt. Brian Parrish of Mesquite Police, "because he paid his bills on time and didn't cause trouble."
His flying hobby appeared to come to end in 2010. Because of his age, Paddock would have been required to renew his license every two years, but once it expired in 2010, he never sought application to renew his licenses, said an Federal Aviation Administration official.
Paddock's aversion to human contact, the real estate broker said, was in part why he preferred playing video poker, a type of gambling that doesn't require interaction with other players. Paddock's wardrobe did not bespeak of a man of wealth, said the broker. Paddock often went out unshaven, in sweats and flip flops, even on his thrice-weekly excursions to casinos, where he ate at the buffet.
Jonathon Speece, a gunsmith at Guns & Guitars in Mesquite, Nev., where Paddock had purchased weapons, said he had met Paddock several times over the last year and never found him to be out of the ordinary.
Paddock, who had a home in Mesquite, never made any statements suggesting a hint of coming violence, Speece, 41, said in an interview at the gun shop.
"He was just like anybody else," Speece said. "All of the locals around here are asking why he did it. Nobody has any answers. It doesn't make sense. I don't think I'll ever understand it."
As authorities pieced together Paddock's life, they were assessing if he hoped to escape from the hotel alive, if anyone helped him and if he planned other attacks before firing upon the country music festival Sunday night.
The most significant might have been in Chicago, where Paddock reserved space in the Blackstone, a 335-room high-rise hotel overlooking the Lollapalooza music festival in August, according to two people familiar with the investigation. A hotel representative said someone reserved a room under Paddock's name but did not stay in the hotel during the festival.
Lollapalooza, which draws an estimated 100,000 people each day, was held in Chicago's Grant Park. Among those in attendance was Malia Obama, the older daughter of former president Barack Obama.
While investigators puzzled over Paddock's potential interest in other concerts, they sought answers from those who knew him. On Wednesday, FBI agents interviewed Marilou Danley, Paddock's girlfriend, hoping she could provide insight.
Danley, who was out of the country during the shooting, told investigators that Paddock bought her a plane ticket to the Philippines to visit relatives. Danley said Paddock then wired her a substantial sum of money and told her to use it to buy a home - which she said made her think Paddock was ending their relationship.
"It never occurred to me in any way whatsoever that he was planning violence against anyone," Danley said in a statement that was read aloud by her attorney. Her attorney did not respond to messages seeking comment Thursday.
According to authorities, Paddock had prepared meticulously and mercilessly. He assembled an arsenal in his suite and, police say, stashed cameras around him to know when officers were closing in.
Speaking Wednesday night, Lombardo, the sheriff, offered the most detailed timeline yet of the incident, describing how officers heard the gunshots, closed in on Paddock's suite and - 75 minutes later - breached the door to find Paddock dead, a handgun not far from his body.
The timeline offered by Lombardo depicts officers desperately trying to rush people inside the hotel to safety. Gunshots first rang out at 10:05 p.m., and seven minutes later, two officers arrived on the floor below Paddock and heard gunfire above them, Lombardo said.
The gunfire ended at 10:15 p.m., police said. Far below, chaos dominated the streets and sidewalks as people fled the venue, scattering to hotels, the airport's tarmac and nearby neighborhoods.
"It was not in one building, it was not in one spot, it was not in one address," Clark County Fire Chief Cassell said. "It was spread over a massive area."
In the hotel, police continued searching for the shooter. At 10:17 p.m., Lombardo said, officers arrived on the hotel's 32nd floor, and just a minute later, a hotel security officer relayed that he was shot. By 10:30 p.m., eight more officers were on the floor, clearing room after room.
At 11:20 p.m., SWAT officers breached the door. They found Paddock's body, Lombardo said. Before they arrived, Paddock had put a gun in his mouth and pulled the trigger. It remains unclear when exactly Paddock shot himself.
