MESQUITE, Nev. — The man who carried out the deadliest shooting rampage in modern U.S. history was a retired accountant with a taste for high-stakes poker who had moved to Nevada just a couple of years earlier.
While investigators were still piecing together the attack by Stephen Paddock at a country music concert that left at least 59 dead and 527 wounded, the gunman's younger brother said the gunman had shown no signs of volatility.
The brother, Eric Paddock, added that he was "dumbfounded" as he searched for an explanation for why his brother, an affluent man — who appeared to be enjoying retired life taking cruises and visiting casinos — would decide to carry out such a brutal attack.
"There's absolutely no way I can even conceive that my brother would shoot a bunch of people he didn't even know," Eric Paddock told the USA TODAY Network in an interview. "There's no rationale. There's nothing anywhere that said why he did this."
Clark County Sheriff Joseph Lombardo said officers determined the gunshots were coming from a room on the 32nd floor of Mandalay Bay complex on the Las Vegas Strip. Authorities said it appeared Paddock killed himself.
Lombardo said 16 weapons were found in the gunman's hotel room. Investigators also found 10 suitcases in the room that they believe were used to bring the arsenal of weapons into the hotel.
Also an undisclosed amount of ammonium nitrate, a type of fertilizer that has been used as a bomb component—most notably in the 1995 Oklahoma City bombing—was found in the suspect’s vehicle parked at the hotel.
Police also found two tri-pods positioned at the hotel windows in what appeared to be a fully-equipped sniper’s nest to take better aim at the crowd below. It appeared he had hammered out the windows of the room before shooting, authorities said.
Hundreds of rounds of ammunition were among the suspect’s possessions, a cache that could have sustained him in the assault, the official said.
"Right now, we believe it's a sole actor, a lone-wolf-type actor," Lombardo said.
Lombardo added that investigators have yet to determine a possible motive for the rampage. "I can’t get into the mind of a psychopath at this point."
Investigators, however, confirmed they have begun probing the gunman's gambling habits. Authorities are reviewing the recent transfers of thousands of dollars involving the suspect and links to gambling activities that would have tripped mandatory government notification requirements, the federal law enforcement official said.
The review is part of wide-ranging search for a possible motive in the attack.
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Investigators believe Paddock used the vantage point to fire on the 22,000 country music fans who gathered for the Route 91 Harvest Festival. He opened fire as the artist Jason Aldean performed.
Lombardo said law enforcement authorities had located a “person of interest” who he named as Marilou Danley, believed to be the suspect's companion.
Lombardo said that Danley was located outside the country. Authorities were already gathering information from her about Paddock, and the sheriff said investigators expected to continue to speak with her once she returned to the U.S.
The Islamic State claimed after the attack that Paddock was one of the terror group's "soldiers." But Aaron Rouse, chief of the FBI’s Las Vegas office, told reporters that investigators have found no links with the gunman to international terror groups.
Eric Paddock said he last heard from his brother via text message to inquire about how their mother was doing after Eric Paddock's Florida neighborhood lost electricity for several days following Hurricane Irma last month. He said that his brother was previously married but had no children.
Paddock added that his brother, who had worked as an accountant before retiring, had "no machine guns" when he helped move him from Florida to Nevada a few years ago.
"It’s like an asteroid just fell on top of our family," he said.
The owners of Guns & Guitars in Mesquite confirmed selling guns to Paddock more than once. But Janis and Mike Sullivan, the co-owners of the shop, noted they do not sell automatic weapons and are not licensed to do so.
“He passed every federal background check, every time he bought a gun,’’ Janis Sullivan, 67, told USA TODAY while standing behind the front-porch screen door of their house in Mesquite
Paddock told the USA TODAY Network that their late father, Benjamin Paddock, was a convicted bank robber and they were raised without him for most of their childhood.
Benjamin, a garbage disposal salesman who was known as "Chromedome," "Big Daddy" and "Old Baldy," committed an armed robbery of a Phoenix bank in 1960 that netted him more than $4,600, the Tuscon Daily Citizen reported in 1971.
He later escaped from a Texas prison and for a time was on the FBI's Most Wanted List. He was captured in 1978 in Oregon, where he was running a bingo parlor.
The most-wanted poster that was first issued by the FBI in 1969 indicated that the father was “psychopathic” and “very dangerous” after escaping from a Texas prison. A federal law enforcement official, however, said that Benjamin Paddock’s past may have no relevance to his son’s actions.
Eric Paddock said, to his knowledge, his brother didn't have a history of mental illness or substance abuse. He said his brother owned guns and played high-stakes video poker.
In recent years, Paddock said they had gone skeet shooting and gambling together, but he had not detected anything was amiss.
But he also described his relationship with his brother as being somewhat distant. He said Stephen barely knew his children and he talked to him only every once in a while. He said he did not know Stephen's girlfriend well.
Eric Paddock did not offer details about his brother's career as an accountant, describing them as "normal, everyday guy jobs."
The gunman worked for the predecessor company of aerospace and defense giant Lockheed Martin from 1985 to 1988, the company said in a statement. The company did not release further details about his employment there.
Police blocked off the road to the suspect’s home in Mesquite, 80 miles northeast of Las Vegas. Records show that Paddock bought the home on Babbling Brook Court in 2015.
The Las Vegas Metropolitan Police Department obtained a search warrant and officers searched Stephen Paddock's home, said Quinn Averrett, public information officer for the Mesquite Police Department.
When law-enforcement agents completed an initial sweep of Stephen Paddock's home Monday morning, investigators found 18 additional weapons and thousands of rounds of ammunition, police said.
Investigators continued to search the residence, and FBI agents arrived at Stephen Paddock's property in Reno Monday morning.
Susan Page, a neighbor at the Reno home, described Paddock and his companion as "closet people" who "kept to themselves."
"I never saw them," she said of her neighbors.
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The house in Mesquite is in a retirement community, Sun City Mesquite, an upscale development of about 1400 homes. The community includes an 18-hole golf course, indoor and outdoor swimming pools and a recreation center. Residents must be at least 55 years old, and no children are allowed.
He owned a home in a 55 and older community from 2013 to 2015 in Viera, Fla., but he rarely stayed there, according to neighbors. The gunman also previously lived in Mesquite, Texas. He sold his home in the North Texas town in 2010
“He seemed normal, other than that he lived by gambling. He was very open about that," said his former Viera neighbor Sharon Judy. "First time we ever met him, he handed us the key to the house and said, 'Hey, would you keep an eye on the house, we’re only going to be here every now and then.'"
Peter reported from Nevada, Glenn from Orlando, Johnson from Washington and Madhani from Chicago. Contributing: Tess Sheetz, Wayne T. Price, Sarah Litz, Kevin McCoy, John Bacon and A.J. Peretz.