By all accounts, up until the very moment he opened fire, Syed Farook, one of the two alleged perpetrators of America’s latest gun-slaughter, was what the gun lobby lionizes as a “good guy with a gun.” Farook, along with his wife, Tashfeen Malik, allegedly killed 14 people at his office’s holiday party in San Bernardino, California, on Wednesday—the 355th mass shooting on the 336th day of 2015. But the couple had had no previous contacts with the law, according to San Bernardino Police Chief Jarrod Burguan. Neighbors and co-workers described Farook as quiet and polite. He had held a stable, middle-class job as a food inspector for five years. Patrick Baccari, who shared a cubicle with Farook, told the Los Angeles Times that the Illinois native and his family appeared to be “living the American dream.”

It remains a possibility that this was an act of Islamic terrorism. CBS reports that the couple had stockpiled 12 pipe-bombs and thousands of rounds of ammunition in their suburban home. But the fact that Farook shot up his co-workers wasn’t on the radar of counter-terrorism officials and that no group has claimed responsibility for the attack doesn’t appear to fit the pattern. Multiple overlapping motives for their rampage could be at play. Regardless of what motive ultimately comes out, the reality is that Muslims have committed only a minuscule fraction of the mass shootings in this country.

We don’t yet know what set off this latest bloodbath, but we know a lot about gun violence in America.

We know that our mental-health care system is indeed broken. But the gun lobby’s ubiquitous claims that fixing it will address the scourge of gun violence are merely a distraction from the real issue. Epidemiological studies show that the vast majority of the mentally ill aren’t violent. They tend to kill themselves at a disproportionate rate. Duke University psychiatrist Jeffrey Swanson told Health Day that people suffering from those kinds of mental-health problems are responsible for only 4 percent of the gun violence in America.

Ultimately, talking about mental illness obscures the real problem: We’re awash in firearms and refuse to take the steps needed to keep them out of the wrong hands.

Perhaps the most frightening thing we know about gun violence comes from a study conducted by researchers at Duke, Harvard, and Columbia that was published earlier this year in the journal Behavioral Sciences and the Law. It found that almost one in 10 Americans who have access to guns are also prone to impulsive outbursts of rage. Among this group are almost 4 million people who carry their guns around in public and say they “have tantrums or angry outbursts,” “get so angry [that they] break or smash things” and lose their temper and “get into physical fights.” The researchers also found that those who own many firearms are significantly more likely to exhibit signs of uncontrollable anger than people who own just one. The authors of the study noted that very few among that group had been diagnosed with the kinds of mental illness that would be unearthed in a standard background check. They say that we need to start restricting gun ownership based on whether people have a history of violence, not on diagnosed mental illness.

We know that Syed Farook had a longstanding interest in guns. CNN reports that he bought at least two of the guns, legally, three or four years ago. In an online profile, he wrote that he “enjoys traveling and just hanging out in the back yard doing target practice with his younger sister and friends.”

Easy access to guns lies at the heart of the problem. No other developed country has as much gun violence or experiences mass shootings at a rate even close to approaching our own, and that we have the highest rate of private gun ownership in the world. We know that out of 185 mass shootings over a 13-year period studied by the FBI, only one was stopped by an ordinary civilian with a gun.

We also know that having access to a firearm almost doubles one’s chances of becoming the victim of a homicide, and triple’s one’s likelihood of killing him or herself. And we know that states with the highest rates of gun ownership have the highest rates of gun murders. The same is true of countries—more guns equal more gun deaths. The incidence of mass shootings has tripled over the past four years, a period that coincided with 37 states’ loosening their restrictions on owning and carrying guns.

As of this writing, what set off Wednesday’s massacre in San Bernardino remains a mystery. But while mass-shooting incidents represent only a small fraction of all the gun violence in America, they’re nonetheless commonplace. And it seems that far too many Americans appear to be willing to accept a certain amount of bloodshed—as long as it’s not perpetrated by Muslims.