The man who killed at least 59 people and injured more than 527 in Las Vegas is a terrorist.

And he’s a terrorist who could operate under the radar because few would suspect a white man to be tangled up with the Islamic State militant group (ISIS).

That could explain why Stephen Craig Paddock, 64, was able to get 16 rifles and hundreds of rounds of ammunition into the Mandalay Hotel, and why he was able to hole up for three days without raising the suspicions of the cleaning staff.

Paddock blended in with the Las Vegas crowds.

Whereas Omar Mateen — the terrorist responsible for the Pulse Nightclub massacre in which 50 people were killed and 58 were wounded — stood out. Before the massacre, Mateen had been investigated as a threat because of comments he made to co-workers.

Donald Trump, then the presumptive Republican candidate for the presidency, used the Pulse Nightclub tragedy to reiterate his call for a “temporary ban on Muslims entering the United States.”

But what do you say when a well-to-do white man stands in a window and fires at thousands of country music fans like he’s shooting ducks in a barrel?

“An “act of pure evil,” Trump said on Monday.

It also is domestic terrorism.

Eric Paddock is adamant that his brother did not belong to a terrorist or hate group.

“He’s just a guy. He lived in Las Vegas. He played at the casinos. There’s nothing. That’s what’s so bizarre,” the distraught brother told reporters.

“No trouble with the law. No mental illness. He was a wealthy guy playing video poker . . . on cruises,” the brother said, shrugging his shoulders in frustration.

That would make him the perfect terrorist. After all, who would suspect a guy like that being capable of mass murder.

But on Monday, the FBI was quick to dismiss ISIS’ claim that it was behind the horrific mass shooting.

“We have determined at this point no connection to an international terrorist organization,” the FBI told the New York Post.

For now, Stephen Paddock is being described as a “shooter,” and a “lone wolf,” as law enforcement officials try to find a motive that could explain why a seemingly “normal” guy would launch such a deadly attack.

Whatever the motive, America has been dealt an agonizing blow.

“If he had killed my kids, I couldn’t have been more dumbfounded,” Eric Paddock told reporters.

“I mean he was not an avid gun guy at all. The fact that he had those kind of weapons . . . he had no military background . . . he’s a guy that lives in a house in Mesquite,” Eric Paddock said, as if that excluded his brother from possibly being a terrorist.

Guns & Guitars, a gun shop, where Las Vegas gunman Stephen Paddock allegedly purchased firearms in Mesquite, Nevada. | Gabe Ginsberg/Getty Images

Something changed dramatically because Stephen Paddock didn’t suddenly run amuck.

“He was planning this for a long time. These were fully automatic firearms. You can’t even buy those in Illinois. I think you can buy them in Nevada, but they are federally licensed,” said Richard Pearson, executive director of the Illinois State Rifle Association.

“They had to be licensed by the FBI. So far there is no evidence of that. He must have gotten these things off the black market,” he said.

Pearson also pointed out that Paddock could only fire these automatic weapons for a minute.

“They get too hot and you have to change the barrel on them or the barrel would melt. These guns came from an illicit source, that’s my guess,” he said.

Stephen Paddock may not fit the profile of a terrorist, but he acted like one.

That makes this the scariest mass shooting thus far.