“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.”