Even before the victims are counted and the blood dried after mass shootings, the public, press, and politicians all begin searching to understand what drove the perpetrators. This is important as a matter of law enforcement—Did they work alone? Is there a remaining threat?—and to make sense of the senseless. But it also serves an important psychological purpose: If the killer can be fit into a known profile, it provides some minimal comfort to an otherwise horrifyingly random crime, some feeling that the key to preventing the next tragedy is just doing a better job of recognizing people like him (it’s almost always a him) and stopping them.

It’s one thing to tell people, “If you see something, say something,” but if no one sees anything, it won’t help. That’s one reason that Stephen Craig Paddock, the man police have identified as the shooter in the Vegas massacre, which killed at least 59 people, is such a frightening enigma. His motivations are, as yet, entirely opaque. As countless people pointed out Monday, Paddock does not immediately fit the “profile” of a mass shooter. More accurately, he does not fit any of the obvious profiles.

Here’s what we do know about the man. He was 64 years old, and lived in Mesquite, Nevada, a town 80 miles northeast of Las Vegas. His brother Eric said he was well-to-do, a millionaire even, and he owned two single-engine planes. He lived in a clean, neat retirement community next to a golf course. Eric Paddock said his brother had moved to Nevada from Central Florida because he hated the humidity and because he loved to gamble; gaming was apparently his main occupation, though he had previously worked as an accountant or auditor and real-estate speculator. He had also lived in Texas, and according to The New York Times owned several other properties around the country. Police said his house in Mesquite was in good order.

“No one seems angry here. Everyone seems happy. Everyone waves,” a neighbor told The Nevada Independent. “Living in this kind of community, you don’t expect that. [It] is just unbelievable.”

Of course, reactions like this are a staple of post-atrocity coverage: With some rare and notable exceptions, few people expect that their next-door neighbors are mass-murderers in the making, and if they do believe that, they sometimes take action or move.

Yet in Paddock’s case, based on what little is known so far, the reaction seems more warranted. For example, Paddock was not a young man, as many mass shooters are, though as a white man he shares a race and gender with many other perpetrators. In the aftermath of the massacre, ISIS claimed credit, perplexing experts who noted that on the one hand, the group’s claims are generally borne out, but that on the other, Paddock was an unlikely ISIS recruit. The federal government says it has not turned up any evidence of ties between him and ISIS.

So far there is no indication that Paddock was part of any other extremist groups, whether on the far left or far right, nor that he belonged to ethnic or racial hate groups. Such affiliations sometimes lead people with superficially contented lives to do terrible things, but that won’t help explain this particular crime.

Sometimes those who commit crimes like this turn out to have been lifelong ne’erdowells, who outdid themselves with one final crime. While Paddock seems to have been solitary and itinerant, he was apparently financially successful, and he had no criminal record. This year, Paddock passed criminal background checks while buying guns, according to stores that sold the weapons to him. Other shooters are frustrated attention seekers who desire infamy, but nothing about Paddock’s background so far makes him fit that description either.

Or perhaps Paddock was mentally ill? It’s tempting to say that anyone who could have committed an act like the Vegas massacre must be unwell. “I can’t get into the mind of a psychopath,” Clark County Sheriff Joseph Lombardo said when asked about motive.

“He’s a sick man, a demented man,” President Trump said Tuesday morning, though he did not offer any more detail. “A lot of problems, I guess. We are looking into him very, very seriously. But we’re dealing with a very, very sick individual.” House Speaker Paul Ryan accented the need for mental-health care Tuesday morning.

Yet there is so far no evidence to support the idea that Paddock was mentally ill, and his brother said he didn’t know of any. Besides, the idea of a link between gun violence and mental illness is, at the very least, probably exaggerated in the public imagination.

“Surprisingly little population-level evidence supports the notion that individuals diagnosed with mental illness are more likely than anyone else to commit gun crimes,” an American Journal of Public Health article found in 2015. “According to Appelbaum, less than 3 percent to 5 percent of U.S. crimes involve people with mental illness, and the percentages of crimes that involve guns are lower than the national average for persons not diagnosed with mental illness.”

Paddock’s gambling habit has raised questions about whether he might have snapped after a losing streak. He was known to gamble large amounts: Eric Paddock showed FBI agents a text in which his brother mentioned winning $250,000, and the Los Angeles Times cited law-enforcement sources who said Paddock had bought at least $10,000 in chips on occasion in the last year, an amount which requires legal disclosure. But the idea of a spontaneous snap occasioned by losses is hard to reconcile with the extensive preparation that the massacre required. Authorities found 23 guns in the Mandalay Bay hotel, from which he opened fire, and there were another 19 at his home, according to police. Some reports suggest he also had tripods equipped for guns. The Associated Press also reported he had devices that can be retrofitted to a semi-automatic gun to increase its effective rate of fire.

Much of the discourse about the massacre has focused on why law-enforcement officials have not labeled Paddock a terrorist. Federal officials use that word to refer to violence perpetrated for a political cause, and so far there’s no evidence to back up its use here. As I wrote after the 2015 attacks in San Bernardino, the FBI was notably deliberate in applying the term there, even after the press had declared the attacks an act of terror. James Holmes’s theater shooting in Aurora, Colorado, sowed terror, but calling it terrorism simply because it was a mass-shooting accident would make little sense.

There are elements of Paddock’s biography that, in hindsight, mark an atypical lifestyle, but hardly the type that ends in blood. He moved frequently. He did not have a typical job—but then again, there is no sign yet that he had problems with money. He was twice divorced—though plenty of people are, and Paddock seems to have had a stable relationship with a woman named Marilou Danley. According to the Los Angeles Times, she was vivacious, and the pair frequented a karaoke bar. (Danley, reportedly an Australian citizen born in the Philippines, was traveling abroad when the shooting occurred, and police are hoping to speak with her, though she is not suspected of involvement.) Paddock’s father was a convicted bank robber who was on the FBI’s most-wanted list after escaping from prison—but again, Paddock himself had no known criminal record.

Some of Paddock’s acquantainces and neighbors suggested he was something of a loner or a recluse. “He was weird. Kept to himself,” a former neighbor told The Washington Post. “We never saw anyone outside there,” another told the Independent. “I questioned whether anyone lived there. The blinds were always drawn.” Yet plenty of others disagree: “He was always normal.” “He was just a nice guy, and that was it.” “He was friendly all the time.”

Eric Paddock, who lives in Florida, has been a major source for information about his brother’s life, and a widely circulated interview that CBS News posted Monday seemed to tap into the strangeness of the situation. There’s no situation in which learning that your brother committed the worst mass-shooting in modern U.S. history won’t be disorienting. (He also says he didn’t know Stephen Paddock to be “an avid gun guy,” and while that’s a subjective determination, the size and type of the arsenal police found suggests more than a hobbyist’s interest.) Yet Eric Paddock’s reactions seem to capture a more essentially perplexing part of his brother’s crime:

“The fact that he had those kind of weapons is just—how the hell did he get automatic weapons?  He has no military background or anything like that,” Paddock said.

Sputtering, shaking his head, and widening his eyes, Paddock tried to reconcile the person he knew with the killer: “He’s a guy who lived in a house in Mesquite and drove down and gambled in Las Vegas. He did … stuff. He ate burritos.”

The banality of that existence makes the Las Vegas massacre even more frightening than even the record-breaking death toll would suggest. The lack of any obvious motivation makes the terror of a random act of violence even deeper and more random. If an ordinary guy, with no obvious ties to extremists groups, no ideological motivations, an apparently placid personal life, stable finances, and no psychological abnormalities—the kind of guy who eats burritos, has a couple beers at the karaoke bar, waves to his neighbors, but largely keeps to himself—can emerge as the deadliest shooter in modern U.S. history, what hope can there be to identify suspects like him before they attack?