As the investigation into the deadliest mass shooting in modern US history enters its second day, local and federal law enforcement agencies are struggling to answer one of the most fundamental questions about the shooter, 64-year-old Mesquite, Nevada resident Stephen Paddock:
Namely - why would a millionaire real-estate investor with no known affiliations to controversial religious or political groups commit such a horrifying act?
The gunman, identified as Stephen Paddock, 64, left no immediate hint of his motive for the arsenal of high-powered weaponry he amassed, including  guns, or the carnage he inflicted on a crowd of 22,000 attending an outdoor country music festival.
Paddock was not known to have served in the military, or to have suffered from a history of mental illness or to have registered any inkling of social disaffection, political discontent or radical views on social media.
Police have said they believed Paddock acted alone, but have been at a loss to explain what might have precipitated the shooting, which left nearly 60 people dead and more than 500 people injured after the shooting sparked a stampede and the 20,000 attendees at the Route 91 Harvest festival rushed for the exits.
The shooter's brother, Eric Paddock
“We have no idea what his belief system was,” Clark County Sheriff Joseph Lombardo told reporters. “I can’t get into the mind of a psychopath.”
No one knows what inspired Paddock to inflict such mass tragedy. But based on what authorities have found, he may have been planning something even worse. Police discovered several pounds of ammonium nitrate, a material used to make explosives, in Paddock's car.
Another angle popularized by some conservative media organizations was that Paddock was motivated by far-left groups like Antifa, amid rumors that Antifa-related "materials" were found in his hotel room.
Initially, ISIS claimed responsibility for the attack, saying Paddock converted to Islam months ago. However, federal law enforcement officials said they haven’t uncovered evidence of any links between Paddock and Islamic State, or indications that he was affiliated with any terrorist organization, or Antifa.
According to WSJ, It wasn’t immediately clear what Paddock, who had once worked at a predecessor firm to Lockheed Martin, most recently did for a living. His brother described him as a wealthy, millionaire retiree who made some of his money through real-estate investments. His brother, Eric Paddock, added that Paddock had no known political or religious affiliations, and that he “was just a guy who liked to go to Vegas and play video poker.”
Police in Mesquite, Nevada, where the shooter lived prior to the attack, had no prior knowledge of the gunman – neither did authorities in a Texas town near Dallas where Paddock had once lived.
"I don't know how it could have been prevented," said Sheriff Lombardo.
Paddock was divorced with no known children.
Eric Paddock, who lives in Orlando, Florida, said he was stunned to learn his brother was responsible, insisting that he must’ve “snapped.”
"We're still just completely befuddled. Dumbstruck."
He described his brother as having "no history of violence. No history of anything couldn't give a s--- less about politics, religion, pointy hatted people etc, etc. He just wanted to get a freaking royal flush." Eric Paddock insisted that he was unaware that his brother had accumulated such an extensive arsenal, and said he’d only ever known him to possess a few handguns, and maybe a rifle, which he had kept in a safe.
Several vigils were held Monday night to honor the victims of the shooting. Community members gathered in Reno, Las Vegas, the Nellis Air Force Base and at the campus of University of Nevada, Las Vegas.
Perhaps more will be revealed in the coming days – though it’s not beyond the realm of possibility that the public may never learn why Paddock did what he did.