He turned the gun on himself before officers were able to break into his room, number 135, in the gold glass skyscraper.
Sheriff Joe Lombardo said authorities believe Paddock put them in place so he could see if law enforcement was coming to try to take him into custody. Another 26 guns were found at two of Paddock's homes.
"He was the least violent in the family during my childhood", Patrick Paddock, the other brother, said of the shooter. "He was a wealthy guy, playing video poker, who went on cruises".
MSNBC has reported that Paddock wired US$100,000 (NZD$140,000) to the Philippines in recent days, the country that his 62-year-old girlfriend was born in and still visited.
Their father, Benjamin Hoskins Paddock, was a serial bank-robber in the 1960s and was on the FBI's 10 most wanted list from 1969 to 1977. In total, across three locations, 47 firearms had been recovered, officials said. He fired incessantly for about 15 minutes on the crowd gathered for the Route 91 Harvest country music festival.
Shocking footage shows terrified revellers fleeing the country music festival held on the famous strip as automatic gunfire can be heard blasting out.
Jason Sorenson, of Newport Beach, California, said he first realised something was wrong when musicians left the stage.
'It was so well lit up because of all the lights of the concert, you could clearly see dozens and dozens of bodies on the ground, just piled up on the ground.
The officials said Paddock was armed with at least 23 firearms. Paddock also set up multiple cameras looking out into the hallway outside the room, apparently to monitor the police response.
Interstate 15 was briefly closed, and flights at McCarran International Airport were suspended.
He owned two planes he was licensed to fly, and was a high roller at Las Vegas casinos, spending up to US$20,000 (S$27,000) daily.
Assistant sheriff Fasulo said Paddock shot a security guard on the 32nd floor of the Mandalay Bay Hotel.
As he departed the White House for Puerto Rico, Trump called the Las Vegas gunman "demented" and a "very, very sick individual". "And it always has". At least 59 people were killed, and over 530 injured in what is now the deadliest mass shooting in United States history.