Steve Marcus / Reuters

The man who opened fire at a music festival in Las Vegas Sunday night notched a ghoulish milestone with the bloodiest mass shooting in American history. But if his attack was unusual in its efficacy, it was less innovative for its approach of killing concertgoers.

In May, an Islamist terrorist killed 22 people at an Ariana Grande concert in Manchester, England. In November 2015, 89 people died in a massacre at the Bataclan in Paris, during a show by the Eagles of Death Metal. Widen the scope just a little farther, and even more examples of killing at cultural events pop up, from the Pulse nightclub shooting in 2016 to James Holmes’s massacre at a 2012 showing of The Dark Knight Rises in suburban Denver.

Attacks in concerts, or in nightclubs and movie theaters, bring with them a special horror, as Alyssa Rosenberg wrote after the Manchester bombing. An attack on an airport is horrific, she noted, but no one chooses to go to an airport in their spare time: It’s either a workplace or a waystation. “By contrast, we choose to go to concerts, to the movies, to sporting arenas and to dinner because of the pleasure they bring us, and the communion we feel in the presence of our community, whether gay men in Orlando or soccer friends in Paris,” she wrote.

That horror is clear not only to attendees, but to attackers. It’s not a surprise that since the Bataclan massacre, which introduced the concert as a tool of modern terror, there have been two bloody attacks on concerts, one in Britain and one in the United States. That there will be more is a virtual certainty. This is because terrorists and other perpetrators of mass violence, whatever their motives, see what works and adopt it. Widespread press attention, which is itself a main goal of mass-casualty attacks, brings public awareness to the methods and can help inform would-be future attackers.

(It is too early to know what motivated the shooter in Las Vegas, whom police identified as Stephen Craig Paddock and said killed himself. ISIS has claimed responsibility for the attack, though as of yet U.S. officials said they had uncovered no links between the shooter and the group.)

“In the United States, school shooters study other school shooters, in particular Columbine,” Peter Bergen, a terrorism scholar at New America, told The Washington Post after the Paris attack. “This is true of terrorists as well. They study tactics that have worked before.”

At that time, Brookings Institution scholar Will McCants warned that terrorism experts were concerned that Paris would augur a shift toward greater use of firearms instead of bombs. “That sounds counterintuitive, but when you’re building the bomb, there’s usually a lot of people involved and you have to buy material that the government has monitored, so it’s easier to identify and disrupt a plot that involves a bomb,” McCants told the Post.

Incidents like Las Vegas, the Pulse shooting, and the 2015 shootings in San Bernadino, California, confirm the lethality of guns, but the dissemination of new tactics has been most apparent over the last two years in the increase in attacks that use trucks or cars not as transportation for bombs but as weapons themselves.

As Colin P. Clarke and Louis Klarevas wrote in The Atlantic in June, the most recent iteration of the tactic seems to have originated in a 2010 issue of Inspire, the magazine published by Al-Qaeda’s Yemeni affiliate. In recent years, vehicle attacks have proliferated widely, from the Middle East to Europe to the United States. Some of the worst include Nice, France, Berlin, and London, though smaller attacks have killed and injured many people elsewhere, including cases that largely escaped widespread attention in places like Quebec or Columbus, Ohio.

The logic behind these attacks is straightforward enough: As authorities have hardened other systems, hijackings have become harder to execute. Guns can be difficult to acquire, depending on where one is. Bombs are dangerous and unpredictable. But almost anyone can get a vehicle and find a crowd. Many of these ramming attacks have been perpetrated by people who claim allegiance to ISIS, but who seem to have had little or no direct contact with ISIS commanders. It’s very easy to learn the technique and act on it without having to travel to a training camp or even undertake risky communication with wanted terrorists.

It’s not just radical Islamist terrorists, though. In June, a man in London rammed a van into congregants at a mosque, reportedly shouting, “I want to kill all Muslims.” Once a tactic’s efficacy has been proven, there’s no reason why only Islamist terrorists would use it. As Mitch Silber, former director of analysis at the New York Police Department, told The Cipher Brief in September:

Showing that a terrorist attack could be very deadly, driving a van and using a knife, makes the argument that even if you prevented or blocked the knowledge about how to make these devices, you still wouldn’t eliminate and maybe not even reduce the threat. So there is really not much that can be done to take away that knowledge once it’s out there, whether it’s on the internet or in the library. Once knowledge is out in the public domain, you can’t put it back in the box. Law enforcement and intelligence can’t monitor everyone who looks at an instruction manual. It’s an overwhelming task.

The spread of ramming attacks and concert shootings follows the pattern followed by other, earlier terrorist tactics. Hezbollah pioneered the modern mass suicide attack in 1983 in Lebanon, with the bombings of the U.S. Embassy and then a U.S. Marine barrack.

For a time, the method spread slowly. Notably, researcher Robert Pape notes, several Tamil Tiger fighters were training in Hezbollah camps at the time of those bombings, and they exported the idea back to Sri Lanka, where suicide bombings became a signature weapon in the island’s bloody civil war. For a time, suicide bombings did not spread widely, but since September 11 and the American invasions of Afghanistan and Iraq, they have become more frequent.

Hezbollah’s suicide truck bombings were, in turn, a variation on the car bomb, an older technique pioneered in the United States, with a 1920 anarchist attack on Wall Street, and adopted around the world.

As my colleague Julia Ioffe wrote after the violence in Charlottesville in August, whether someone is drawn to violence through religious belief, racial animus, or any other motive, the radicalization process tends to follow a consistent and predictable pattern. That is not the only thing that violent attackers, regardless of motive, success, or location, have in common. The growing log of attacks also provides all of them a base of knowledge from which to draw techniques and plan their own.

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