64-year-old Stephen Paddock, a one-time Boy Scout and licensed pilot, had no record of criminal activity before unloading automatic weapon fire on a Vegas crowd of 22,000 gathered for a country music concert.
Speaking from Orlando, the gunman's stunned brother compared news of the attack to an asteroid falling from the sky onto his family.
"I mean, my brother did this. This is like it was done, you know, like he shot us. I mean, if he'd have killed my kids, I couldn't be more dumbfounded," said Eric Paddock who last spoke to his brother six months ago.
An accountant and former employee of a Lockheed Martin subsidiary, Stephen Paddock led a nomadic existence that brought the competitive gambler to Texas as early as 2004.
Records indicate Paddock managed the Central Park Apartments on Houston's South Gessner Road and owned homes and property in the Dallas suburb of Mesquite.
The Houston complex's current management tells FOX 26 no longtime residents have stepped forward with any recollection of the man believed to have committed mass murder.
While Paddock had no detectable connection with any radical group or criminal enterprise his father, Benjamin Paddock, was a convicted bank robber who was included on the FBI's "most wanted" list.
A few years ago, Stephen Paddock, reportedly retired to the Nevada community of Mesquite, purchased a quarter million dollar home and made frequent gambling trips to Las Vegas, 80 miles away.
In the wake of the shooting ISIS announced Paddock as a recent convert to Islam, but provided no proof. The FBI has discounted the claim, leaving motive a mystery.
"I hope someone figures it out, because we would like to know," said Eric Paddock.
Paddock's marriage ended in divorce 27 years ago. His current girlfriend was traveling outside the country at the time of the shooting.
A gun dealer in Nevada confirmed Paddock recently purchased three weapons - two rifles and a handgun.
Turns out, the man now believed to be the most prolific mass killer in American history passed the background check.
"Not an avid gun guy at all. The fact that he had those kind of weapons is just...where the hell did he get automatic weapons? He's not, he has no military background or anything like that. I mean, when you find out about him, like I said, he's a guy who lived in a house in Mesquite and goes down and gambled in Las Vegas," said Eric Paddock.
Fox News is reporting Stephen Paddock had at least 10 weapons in his room including modified AR-15 rifles and high capacity magazines.