Analysis: What Austrian authorities have revealed about the alleged terror plot aimed at Taylor Swift's three Vienna concerts adheres to a chilling pattern familiar to European counterterrorism officials.
The prime suspect is a 19-year-old who was arrested in Ternitz, about an hour's drive from where Swift was scheduled to perform Thursday, Friday and Saturday for an expected 65,000 fans each night at the Ernst Happel Stadium.
The head of Austria's domestic intelligence agency, Omar Haijawi-Pirchner, said the suspect's aim was to "kill himself and a large number of people." In a raid on the suspect's home police found chemical explosives, detonators, ISIS propaganda, knives and machetes. He even had a blue light used by police to attach to their cars, which could have helped him drive to the busy scene.
Two other suspects are being questioned: a 17-year-old who recently broke up with his girlfriend and who worked for a company that provides services to the venue, and a 15-year-old boy who prosecutors are still determining if they were directly involved. All are Austrian-born and have either Turkish, Croatian or North Macedonian backgrounds.
The 19 and 17-year-old suspects had been radicalized online, police said, adding the 19-year-old had sworn allegiance to ISIS' new leader last month.
Police also alluded to the role of social media in both the radicalization of the suspects and alleged planning of the attacks.
"Communication of the perpetrators is undertaken usually in an encrypted form," often masking their conversations from routine counter-terror surveillance, General Director for Public Security Franz Ruf told reporters.
Online chatter to action
The path of online teenage chatter turning to real-world plotting has become alarmingly common in recent months. A study by terrorism expert Peter Neumann showed teenagers accounted for nearly two thirds of ISIS-linked arrests in Europe in the previous nine months.
The study of 27 ISIS-linked attacks or disrupted plots since October last year revealed that of the 58 suspects, 38 were aged between 13 and 19, according to Neumann, professor of Security Studies at King's College London. CNN verified most of Neumann's data with European security officials.
Neumann noted the latest Europol data showed "the number of attacks and planned attacks has more than quadrupled" since 2022.
Among the cases Neumann referenced was another in Austria, in which a 14-year-old girl from Montenegro was arrested in May in the southern city of Graz after buying a knife and axe for an attack she was allegedly plotting. ISIS material was also found on her computer.
Teenagers were also arrested during France's security sweep ahead of the Paris Olympics.
In late May, an 18-year-old man of Chechen origin was indicted for "terrorist criminal association," for alleged plans to target spectators in the city of Saint-Étienne during the Games, according to a statement from French anti-terror prosecutors.
About a fortnight earlier, two teenagers were arrested in northeast and southern France for plotting a terror attack, the target unclear, the statement said.
And in April, a 16-year-old from the Haute-Savoie department in southeastern France was arrested for allegedly researching how to make an explosives belt and die as an ISIS martyr, possibly targeting the Olympics, the statement added.
German police have also publicized two alleged terror plots involving teenagers in recent months.
In April, officials in the western city of Dusseldorf said they arrested two girls, aged 15 and 16, and a 15-year-old boy accused of planning a terror attack.
Another alleged plot involving a possible knife attack on a Heidelberg synagogue, which was disrupted in May, involved an 18-year-old man, a German prosecutor's statement said.
Meanwhile in Switzerland, police in March arrested a 15-year-old Swiss boy and a 16-year-old Italian boy for alleged ISIS support and plotting bomb attacks, according to a police statement.
Neumann, the terrorism expert, said teenagers were often recruited online, where ISIS and its Central Asian affiliate ISIS-K only needed to see success in a handful from hundreds of potential recruits.
"Groups like (ISIS-K are) specifically targeting young teenagers," Neumann said. "They may not be very useful. They may mess up. They may change their mind," he said, but they are "not least less suspicious. Who would think of a 13-year-old as a terrorist? One is enough."
Teenagers were being recruited through social media platforms like TikTok, dragged through algorithms into "bubbles" online where jihadist recruiters can reach them, Neumann said.
ISIS-K was "by far the most ambitious and aggressive part of ISIS right now," plotting complex attacks and recruiting online, he added.
A TikTok spokesperson told CNN last month: "We stand firmly against violent extremism and remove 98% of content found to break our rules on promoting terrorism before it is reported to us."
While details of the alleged plans to attack Swift's concerts remain unclear, European security sources have been increasingly concerned that terror plots are becoming more "directed" – or organized by a more experienced or resourced recruiter from afar.
A British security source told CNN the so-called "directed terror threat" had become a greater concern over the past 18 months, with ISIS-K the most potent group under scrutiny. Young people accessing extremist spaces and media online also continues to be a significant issue, the source said.
European counter-terror officials are also struggling with a fast-morphing terror threat emerging from parts of the former Soviet Union, including Russia's North Caucasus region and Central Asian states like Tajikistan.
Last month, Austrian counter-terror police said they had detained eight men and a woman for fundraising for ISIS. Laptops, cash, fake passports and a vehicle were confiscated, and authorities said the suspects, originally from Chechnya in the Russian Federation, might have their Austrian residence permits revoked.