Over the past decade, America has developed a tragic reputation as the land of senseless mass shootings. And in the wake of last weekend’s massacre at a gay nightclub in Orlando, which left 49 victims dead and an additional 53 wounded, we as a country must ask ourselves how to prevent such tragedies from happening again. And again. And again.

The first step, of course, is to identify a pattern.

While those of us on the left fight for stricter gun control, those on the right argue that “guns don’t kill people, people kill people.” And Republican presidential candidate Donald Trump wants us to believe that, specifically, Muslims kill people. But what happens when we look at the data—who is really behind the shootings?

For the past three-and-a-half years, Mother Jones has been compiling data on every mass shooting in this country since 1982. There have been 81 in total. And of these, a whopping 79 involved a male shooter. That’s right. The common denominator has nothing to do with race or religion or ethnicity—it’s gender. In case these numbers don’t speak for themselves, here’s what this ratio looks like in graphic form:

The only women on the list are Jennifer San Marco, who killed seven people during the Goleta Postal rampage in 2006; Cherie Lash Rhoades, who killed four people (three of which were family members) in 2014, during the Alturas Tribal shooting; and Tashfeen Malik who, along with her husband, opened fire in San Bernardino late last year, killing 14 people.

Of course, this isn’t the first time this pattern has been discussed. Last year, James Garbarino, a professor of psychology and the author of the book Listening to Killers: Lessons Learned From My 20 Years as a Psychological Expert Witness in Murder Cases wrote an opinion piece for CNN in which he presented a devastating fact: 90% of killers in the U.S. are male.

Garbarino points to a variety of factors, including a gene that researchers believe impairs some men’s ability to deal with stressful situations, such as abusive families. Other factors include the prevalence and glorification of male violence in media and a culture of “toxic masculinity.”

“This is vitally important,” Gabarino writes, “because as a society, we often ‘promote’ the various socially toxic cultural messages to which boys and men are exposed—racism, misogyny, the belief that ‘it is better to be mad than to be sad.'”

On Monday, Amanda Marcotte wrote in Salon about how Omar Mateen, the Orlando shooter, may himself have been influenced by toxic masculinity, which she describes as “a specific model of manhood, geared towards dominance and control. It’s a manhood that views women and LGBT people as inferior, sees sex as an act not of affection but domination, and which valorizes violence as the way to prove one’s self to the world.”

James Alan Fox, a criminologist at Northeastern University, expressed a similar sentiment last year, after Dylan Roof killed nine people at a historic black church in Charleston, South Carolina. “Women tend to see violence as a last resort, as a self-defense mechanism. You use violence if you have to, if there’s no other way out,” Fox told CNN. “Men tend to use violence as an offensive weapon, to show them who’s boss.”

Add to this problem the ease of procuring a semi-automatic weapon in this country—and suddenly, you have a lot of angry, unstable men with mass killing potential.

So perhaps Trump—who wants to ban Muslims, deport undocumented immigrants, and build a wall to keep the alleged killers out—needs to take a long, hard look at his own gender. It’s clear that if we really want to stop mass shootings, we need to find a way to stop men.