By now the story is depressingly familiar:

A young man is radicalized by the far-right online ecosystem. That leads him to believe that some “other” group is systematically working to erase the white race. The individual is a lone wolf, staying off law enforcement’s radar until it’s too late, sometimes literally minutes before the attack, when he announces his plans online.

In the latest instance, the attack was targeted at the Chabad of Poway synagogue, near San Diego, on Saturday. The shooting left one woman dead and three others injured, including an eight-year-old girl.

But perhaps the most alarming factor in this latest incident of far-right violence can be found in the open letter that the gunman, a 19-year-old, posted just prior to the attack. The similarities it bears to the manifesto penned by the shooter in New Zealand who targeted mosques last month shows how the motivations and knowledge of previous far-right extremists are being “meme-ticized,” bouncing off of each other and helping to accelerate the rate of attacks.

The use of previous extremists and their manifestos for inspiration by other would-be attackers has long been a persistent theme in the far-right. Anders Behring Breivik, the Norwegian far-right terrorist who killed 77 people — most of them teenagers — in 2011 has long been venerated in far-right circles, and his rambling, 1,500-page manifesto has been cited as inspiration for other far-right extremists. Both Christopher Hasson, the Coast Guard Lieutenant who stockpiled weapons and had a hit list of prominent Democrats and journalists, and the Christchurch shooter, both cited Breivik and his writings as inspiration.

But the Christchurch attacker’s manifesto, where 50 worshipers were killed at two separate mosques, seems to have only further accelerated this process. His 74-page manifesto was filled with smug in-jokes designed to troll those not familiar with the far-right online ecosystem which radicalized him. Less than two months after that incident, the influence of his manifesto is clear to see in the open letter written by the attacker in San Diego on Saturday.

“Information is now moving much quicker, it’s no accident that [white nationalists] have spoken with a sense of urgency and you can see that in [the latest shooter’s] manifesto,” Zahed Amanullah, Resident Senior Fellow at the Institute of Strategic Dialogue, told ThinkProgress. “That sense of urgency comes from a hyper-charged communication landscape. Now these attackers and their supporters and those who were inspired by the attack, they’re amplifying their places online and that’s a real concern.”

“In this case it looks as if they were acting alone in terms of planning but they’re not acting alone in terms of being inspired, gathering information, tactical knowledge, ideology, it’s clear that the pace of that dissemination is increasing,” Amanullah continued. “That’s the real concern because the bar is being lowered and lowered for someone to be inspired by the manifesto and to take action themselves.”

In their manifestos’ diatribes, for instance, both the New Zealand and San Diego shooters take great pains to tout their European heritage. Both manifestos say they want to further polarize the gun control debate, and both respond to anticipated questions about their attacks with in-joke language designed to titillate those in the know and further infect the discourse surrounding the attack. A good example here is the “Subscribe to PewDiePie” meme — which the New Zealand gunman mentions in his livestream of the shooting and the San Diego gunman in his open letter. In response, YouTuber PewDiePie published a video on Sunday — which was #1 on YouTube’s trending videos Monday with nearly 7.5 million views — condemning the use of the phrase. While there’s no reason to question PewDiePie’s renunciation of the meme is anything but heartfelt, the fact that he has been cornered into discussing it at all gives further oxygen to the fringe, far-right online ecosystems which radicalized both shooters.

“The manifestos end up acting like memetic guide for other people… in terms of both the shooting and the manifesto but also in terms of attempts to use memes to radicalize more people,” Becca Lewis, a researcher at Data & Society, told ThinkProgress. “[The mention of PewDiePie] is a perfect example. They’re trying to stoke division and discord between the mainstream media and internet culture and in some ways hoping to bait PewDiePie into radicalizing youth, which anyone under the age of 20 would say that’s ridiculous.”

Perhaps most importantly, however, both shooters used the /pol/ board on the website 8chan to announce their intention to carry out a mass shooting. As investigative news outlet Bellingcat has noted, the combination of white nationalist propaganda, continued calls for violence, and now two successful examples of “real-life effortposting” — i.e. violence that translates over from the internet to the real world — creates the worrying possibility that the type of language the two shooters used will be further “memeticized” and, in turn, used as inspiration for yet another far-right extremist attack. In wake of the New Zealand attack, the founder of 8chan Frederick Brennan himself said that he would not be at all surprised if a similar incident happened again.

“Part of the challenge of this is that we now see twice in the span of a month this platform has been used to announce an impending attack,” Amanullah said. “There’s a pattern now about how you use different platforms to disseminate different messages to different audiences. You have your core believers in 8chan who won’t rat on you and who will cheer you on and then you have your mainstream social media platforms used to spread it further.”

But while the fingerprints of other far-right extremists can be seen on this latest attack, any sort of consensus on how to tackle the problem remains woefully far off. As Amanullah pointed out, the open letter by Saturday’s attacker, as hateful as it is, is not illegal speech, and the open-sourced, lone wolf nature of these attacks makes it virtually impossible to track these individuals as part of a terrorist group. What’s more, while social media companies have made a major effort to limit the ability of groups like ISIS to organize and celebrate online, the same effort has not been made towards white supremacist groups — partly because, by Twitter’s own admission, that would mean that some Republican politicians end up getting banned as well.

Amanullah likened the ability of 8chan and other parts of the far-right online ecosystem to skirt the rules to the British Islamic hate preacher Anjem Choudary. For years Choudary helped to radicalize men who would go on to commit terrorist acts — including the July 7 bombing in London in 2005 — but all while keeping his speeches and rhetoric just outside the reach of U.K. terror laws. He was finally convicted in August 2016, and was released in October 2018 under strict bail conditions.

One of the more obvious solutions here would be to make a major effort to take 8chan off the web. This would seem straightforward, bearing in mind that it is not only a haven for white nationalists, but child pornographers as well. But as Becca Lewis pointed out, this idea quickly runs into several ethical and logistical hurdles.

“I agree that at this point I think that 8chan is just a truly harmful place for humanity, but at the same time there are a lot of tricky ethical questions that emerge in terms of what platforms are allowed to stay online and at what level that stops,” she said. “There are also practical challenges in terms of making it a game of cat and mouse. 8chan emerged as a force after 4chan decided to regulate some of the Gamergate content that got moderated there.”

There’s also the problematic fact that local law enforcement — be it New Zealand, California, or Pittsburgh — is being forced to confront a movement which is by its nature decentralized, international, and which moves at lightning pace on social media.

“It’s really ironic there are these hypernationalist groups and they’re coordinating internationally,” Lewis said. “I think a lot of this comes back to the social networking capabilities of the internet which are facilitated by social media companies which are international but still by and large based in the U.S. and which appeal to U.S. ideas of freedom of speech so you get a lot of complicated forces. It’s a challenge we haven’t necessarily faced before.”

Both Lewis and Amanullah, however, agreed that mainstream social media platforms needed to do more to stop the rot of far-right extremism from spreading onto their platforms. Because while communities like 8chan are far more vitriolic, it’s the ability of these memes and manifestos to spread onto sites like Facebook and Twitter which give them real power. Lewis also noted that media outlets needed to evolve in the way they cover these sort of attacks, to ensure that their manifestos and motives are not given free publicity — which a number of British tabloids notably failed to do in wake of the New Zealand shooting.

“I think one thing that the digital media has enabled is that the nature of memes is that they can travel around world in minutes, and that was absolutely the case in terms of the New Zealand shooting that spread incredibly rapidly as did the Livestream,” Lewis said. “If not done carefully, coverage can inspire copycats and we need to think about that.”

Amanullah also noted that, in wake of the ISIS attacks on churches in Sri Lanka on Easter, there was very little immediate understanding of who had carried out the attack and why, partly because social media companies had made such an effort to clamp down on the spread of ISIS-linked propaganda online.

“We’re hoping to see people turn their eyes towards white supremacy, because that’s much more infecting of the mainstream,” Amanullah noted. “The danger is that all of this experience and knowledge is being aggregated for the next shooter.”

This post has been updated to clarify Mr. Amanullah’s comments on the Sri Lanka attack.