Alex Yablon is a reporter for The Trace, a nonprofit journalism outlet devoted to guns in America.

A student and her mother embrace one another in San Bernardino, Calif., where a school shooting took place April 10. (Frederic J. Brown/AFP)

It is now just two weeks into September, and the month has already seen its share of mass shootings. At a Dallas Cowboys watch party in Plano, Tex., a woman’s estranged ex-husband murdered her and seven of her friends; and on Wednesday, in Rockford, Wash., a gunman opened fire at a high school, killing at least one and injuring at least three.

For the past two years, I’ve covered killings like these as a reporter for the Trace, a nonprofit journalism outlet dedicated solely to covering guns in America. I’ve become accustomed to the standard public discussion that follows mass shootings: What could have possibly motivated such senseless acts of violence? School shootings in particular tend to generate plenty of political debate, either about the shooters’ beliefs (occult activity in Christopher Harper Mercer’s case; violent video games and music in Eric Harris and Dylan Klebold’s; misogyny, masculinity and entitlement in a host of others) or the role of firearms in their lives.

But my experience suggests that the outsize attention paid to the shooter’s particular beliefs obscures the real connections between mass shooters. What binds them together and elevates their likelihood of killing in this particular fashion is a history of antisocial, sometimes violent conduct, not any particular belief set.

The Trace launched just 48 hours after the 2015 Charleston church massacre. Since then, my colleagues and I have covered similar shootings perpetrated by failed business owners, wayward veterans, troubled teenagers, jihadist dabblers, disgruntled employees, antiabortionists, estranged spouses, Black Lives Matter supporters, sovereign citizens and many others. It’s usually difficult to decide just which label best describes the perpetrator: Often, several seem to apply, or none at all. The difficulty of interpreting motivations is compounded by the fact that at the end of these rampages, the shooter is typically among the dead.

What is clear, however, is that regardless of ideological motivation, or even in the complete absence of any such drive, these kinds of attacks are usually presaged by some clear warning signs.

As Duke University psychiatrist Jeffrey Swanson told me in the wake of the 2016 Pulse Nightclub shooting in Orlando, “Most people who commit serious crimes, that’s not where they began. They didn’t just start committing gun homicides.”

Before shooters actually kill, they usually assault, abuse or threaten people close to them, such as spouses or co-workers. They are often profoundly alienated from society. James T. Hodgkinson, who opened fire on a Virginia baseball field last summer, for instance, threatened his daughter with a knife, punched his neighbor in the face and struck his neighbor’s boyfriend with a shotgun before firing a round at the man as he fled. In the months running up to the shooting, he lived out of a van nearly a thousand miles from his Illinois home. Likewise, Omar Mateen, who committed the Orlando shooting, routinely beat his first wife, threatened co-workers and could barely hold down a job. Even those shooters without violent histories, such as Dylann Roof, Elliot Rodger or Seung-Hui Cho, were known by friends, family or teachers to make disturbing threats and had withdrawn from normal social life.

The number of people who engage in this kind of antisocial behavior is dwarfed by the number who hold strong beliefs about politics, society or religion. With that in mind, Swanson of Duke told me that scrutiny of a mass shooter’s political convictions or media diet is about as useful as that applied to violent video games or the music of Marilyn Manson after the 1999 Columbine shooting.

Despite the fact that mass shooters often fit a clear profile, our background-check system is ill-equipped to stop people like this from buying guns. Even though in 32 states they could easily buy a gun in an unregulated private sale, many actually pass background checks to buy their murder weapons.

While their personalities may unsettle family members or acquaintances, mass shooters rarely meet the federal criteria for being deemed mentally unfit to purchase a weapon. A diagnosis or even an inpatient stay at a psychiatric hospital is insufficient. The background-check system blocks people from buying guns only if a court, board, commission or other lawful authority deems them mentally ill. People committed by family members aren’t flagged and may buy guns. In any case, a propensity for anger is not, strictly speaking, mental illness, and the mentally ill are far more likely to be victims of violence or to harm themselves than they are to harm others.

Similarly, while many mass shooters may threaten or even physically harm other people before taking up a gun, they are rarely found guilty for crimes that would bar them from buying or possessing a firearm. Domestic violence, one particularly common precursor to mass shootings, is notoriously difficult to prosecute. Other kinds of antisocial behavior may not actually be crimes, or only low-level misdemeanors, even if clinicians consider them glaring red flags.

Facing these challenges, a handful of states have tried to adjust. California, for instance, expanded the range of criminal violations that prohibit residents from buying guns to include violent misdemeanors like assault. Assault doesn’t carry the potential for a lengthy prison sentence, so it’s not recognized by the federal background-check system, even though a conviction can be a clear warning sign. But California adds an extra layer of scrutiny to gun buyers’ conduct.

Some states have created so-called Gun Violence Restraining Orders. These orders allow family members or police to petition a court to temporarily seize a person’s guns if they pose a threat to themselves or others. They are issued in civil, not criminal, courts, so they do not require a criminal court’s much higher burden of proof. These proceedings also allow the gun owner redress. They can appeal the order, or wait a given length of time to come back to court, demonstrate they are no longer dangerous and get their guns back.

These are highly targeted interventions based on empirical research that respect due process. They would not affect the vast majority of gun owners, or those who mouth off online, for that matter. Nonetheless, the National Rifle Association has repeatedly opposed the expansion of policies like these. It applauded Supreme Court Justice Clarence Thomas’s suggestion that the federal ban on gun possession for people convicted of misdemeanor domestic violence is unconstitutional.

This is not to say what someone believes does not sometimes lead directly to bloodshed. Beliefs have motivated violence for centuries: When leaders explicitly advocate or condone violence, social movements or cells organize to brutally confront opponents or carry out assassinations, or attempts to raise awareness of this risk are deliberately ignored. But if we want to stop mass shootings before they happen, it isn’t extreme beliefs or motives we should be focusing on — it’s the antisocial, violent and threatening behavior, ideological or not, of those around us.