Three days after a gunman unleashed an 11-minute stretch of gunfire upon a crowd of 22,000 concertgoers from his perch on the 32nd floor of a Las Vegas hotel, investigators remain dumbfounded by the lack of clues about his motive.
Stephen Paddock, a 64-year-old retired accountant, had no prior criminal record, left no social-media footprint, and had not established any apparent ties to extremist groups, officials say. His attack was the deadliest mass shooting in modern US history, killing 58 and leaving more than 500 injured.
But what authorities have made clear so far is that Paddock methodically planned every detail of his attack, ensuring he had a massive arsenal of weapons outfitted to maximize carnage, and a network of cameras set up inside and outside his hotel room, presumably to alert him when law enforcement arrived to take him down.
"I anticipate he was looking for anybody coming to take him into custody," Clark County Sheriff Joseph Lombardo told media Tuesday afternoon. "It was preplanned, extensively, and I'm pretty sure that he evaluated everything that he did in his actions, which is troublesome."
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Paddock checked into his suite at the Mandalay Bay Resort and Casino on Thursday. Over the next few days, he hauled up at least 10 suitcases filled with firearms, though hotel staff members said they spotted nothing "nefarious," Lombardo said.
He kept the "do not disturb" sign on his door throughout his stay so no staff members would enter, an unnamed hotel worker told The New York Times.
Paddock amassed his weapons cache over a period of years, purchasing them legally in Nevada, California, Utah, and Texas, officials said. When investigators entered his room, they found 23 guns, including AR-15-style and AK-47-style rifles, and a hammer Paddock had apparently used to smash two of the hotel suite's windows.
Twelve of the rifles recovered from Paddock's suite had been retrofitted with "bump stock" devices, which enable semiautomatic weapons to achieve rapid-fire capabilities, an agent with the Bureau of Alcohol, Tobacco, Firearms, and Explosives told media on Tuesday.
Authorities recovered an additional 24 rifles, shotguns, and pistols from two Nevada properties owned by Paddock. He had purchased 33 firearms in the past year alone.
Beyond the weaponry, Paddock appears to have planned the rampage down to the moment police stormed his suite. He set up an elaborate surveillance system, placing cameras in the hallway outside his suite, on a food-service cart, and over the peephole of his door, officials said.
The cameras appear to have been effective — Paddock at one point shot through his suite door and wounded a security guard. Paddock eventually turned one of his guns on himself, pulling the trigger as a SWAT team closed in around his suite.
Even the absence of Paddock's girlfriend, Marilou Danley, who traveled to the Philippines a week before the shooting, appears to be part of his plan, her sisters say. Danley, whom authorities are questioning as a person of interest, arrived back in the US late on Tuesday night and was escorted away by FBI officials.
"She was sent away so that she will be not there to interfere with what he's planning," one of Danley's sisters told Australia's Channel 7 TV network. The network withheld both sisters' names.
Paddock's brother Eric Paddock offered a similar theory.
"He manipulated her to be as far away from here and safe when he committed this," he told The Washington Post. "The people he loved he took care of, and as he was descending into hell he took care of her."