Shortly after 1 am on Sunday, an apparent dispute between several people at the Cameo nightclub in Cincinnati escalated — leading to a shootout that left one person dead and 15 wounded.

Authorities have said that the attack was not related to terrorism. The club has a history of gun violence, including a New Year’s Day shooting in 2015 and another shooting in the parking lot in September of that year, according to the Guardian. The club has security measures in place to try to stop patrons from bringing in guns, but some firearms apparently made it through.

Police do not have any suspects in custody, but they are still interviewing witnesses. “It was just a lot of chaos, obviously, when the shots went off,” Cincinnati Police Department Capt. Kimberly Williams said. “People [were] just trying to get out of harm’s way.”

Based on what we know so far, this weekend’s incident doesn’t seem like the mass shootings or terrorist attacks we’ve seen over the past few years. Instead, it seems like it began almost run-of-the-mill — an interpersonal dispute that spiraled completely out of control.

That doesn’t make the attack any less horrific. As Cincinnati Mayor John Cranley said, “What difference does that make to the victims? Innocent people were shot.”

It does, however, make the attack demonstrative of how the prevalence of guns in America leads to gun deaths: When firearms are within arm’s reach, what would otherwise be a petty dispute between family members, friends, colleagues, or peers can quickly escalate into a deadly confrontation. And, tragically, this is a uniquely American problem in the developed world.

More guns mean more gun deaths

No other developed country in the world has anywhere near the rate of gun violence that America has. The US has nearly six times the gun homicide rate of Canada, more than seven times Sweden’s, and nearly 16 times Germany’s, according to United Nations data compiled by the Guardian. (These gun deaths are a big reason America has a much higher overall homicide rate, which includes non-gun deaths, than other developed nations.)

What’s more, there appears to be a correlation between America’s high levels of gun violence and gun ownership, as this chart from Tewksbury Lab shows:

Research reviews by the Harvard School of Public Health’s Injury Control Research Center have concluded that more gun ownership leads to more gun violence. Studies have found this to be true again and again — for homicides, suicides, domestic violence, and violence against police. Other factors (such as socioeconomic issues) contribute to violence, but guns are the one issue that makes America unique relative to other developed countries in comparable socioeconomic circumstances.

What we currently know about the Cincinnati nightclub shooting fits into this pattern. Disputes at nightclubs are, on their own, fairly mundane. In the absence of firearms, one is not very likely to turn fatal. But in America, guns are by and large readily available, and that means it’s more likely someone will be able to pull out a gun and kill someone in a moment of rage.

This happens in far more contexts than just nightclubs, of course. It happens in family disputes, school interactions, conflicts between gangs, and so on.

That’s one reason why where there are more guns, there is more gun violence. Here’s one chart, from a 2007 study by Harvard School of Public Health researchers, showing the correlation between statewide firearm homicide victimization rates and household gun ownership after controlling for robbery rates:

A more recent study from 2013, led by a Boston University School of Public Health researcher, reached similar conclusions: After controlling for multiple variables, the study found that a 1 percent increase in gun ownership correlated with a roughly 0.9 percent rise in the firearm homicide rate at the state level.

And this holds up around the world. As Zack Beauchamp explained for Vox, a breakthrough analysis in the 1990s by UC Berkeley’s Franklin Zimring and Gordon Hawkins found that the US does not, contrary to the old conventional wisdom, have more crime in general than other Western industrial nations. Instead, the US appears to have more lethal violence — and that’s driven in large part by the prevalence of guns.

“A series of specific comparisons of the death rates from property crime and assault in New York City and London show how enormous differences in death risk can be explained even while general patterns are similar,” Zimring and Hawkins wrote. “A preference for crimes of personal force and the willingness and ability to use guns in robbery make similar levels of property crime 54 times as deadly in New York City as in London.”

This helps explain why rigorous reviews of gun policies have concluded that stricter gun laws can reduce gun violence and deaths: A 2016 review of 130 studies in 10 countries, published in Epidemiologic Reviews, found that new legal restrictions on owning and purchasing guns tended to be followed by a drop in gun violence — a strong indicator that restricting access to guns can save lives.

Taking all of this together, the empirical research seems clear: Where there are more guns and more access to guns, there are more gun deaths. And until policymakers do something about that, we can expect more incidents like the Cincinnati nightclub shooting.