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Input: The attack  at least initially  was as inexplicable as it was horrifying. Law enforcement officials said they could not immediately tell what drove  Stephen Paddock  to fire at thousands of unsuspecting concertgoers from the 32nd floor of the Mandalay Bay Resort and Casino before killing  himself .
Authorities said a sweep of law enforcement databases showed  Paddock  had no known run-ins with police  and â despite the Islamic Stateâs repeated claims otherwise â investigators also could not find any connections to international terrorist groups. He was the son of a notorious bank robber and his own crime demonstrated some amount of sophisticated planning.
Police said  he  stayed in a large hotel suite for several days and aroused no suspicion  bringing with  him  an arsenal of 23 guns â their calibers ranging from .223 to .308  some with scopes â authorities said. One of the weapons  he  apparently used in the attack was an AK-47 type rifle  with a stand used to steady it for firing  people familiar with the case said.  He  fired  without warning  from an elevated position on an open-air venue  leaving  his  victims few options to avoid harm.
Stephen Paddock was identified by police as the gunman in the deadliest mass shooting in modern U.S. history. Here's what you need to know about him. (Monica Akhtar/The Washington Post)
[Las Vegas gunman Stephen Paddock enjoyed gambling  country music  lived quiet life before massacre]
Police and hotel security ultimately scoured several floors of the hotel looking for the shooter and came upon Paddockâs suite  Lombardo said. At some point   Paddock  fired through the door and hit a security guard in the leg   he  said  adding that the guard is expected to survive. SWAT officers ultimately stormed the room and some fired shots  though  Paddock  is believed to have killed  himself   Lombardo said. He was not counted in the death toll that authorities reported.
Eric Paddock  Stephen Paddockâs brother  said he was stunned to learn that his brother could be responsible for such violence.
Stephen Paddock had no history of mental illness nor did he have problems with drugs or alcohol  Eric Paddock said  noting that his brother was a high-stakes gambler  sometimes wagering hundreds of dollars on a single hand of video poker.
Eric Paddock said his brother was âwealthy â in part because he had no children to support. Stephen Paddock had worked in the past as an accountant  and he had real estate investments in the Orlando area  Eric Paddock said.
Relatives said Stephen Paddock  a licensed pilot who owned two airplanes  was a quiet man who often went to Las Vegas to gamble and view concerts. In a statement  Lockheed Martin  the defense giant  said that Paddock worked for them for three years in the 1980s.
 A former neighbor of Stephen Paddockâs  recalled that  his  home in a 55-and-over community in Florida looked more akin to a college freshmanâs dorm  with nothing on the walls and only a few pieces of furniture.

Las Vegas massacre: Gunman Stephen Paddock  amassing small arsenal kills at least 58 and injures more than 500