BERLIN—A European terror suspect has never been so young.

The stalkers of the so-called Islamic State have been searching out, grooming and inciting young terrorists in France and Germany for more than a year now, and in the latest shocking incident, they appear to have used a boy who’s only 12 years old.

On Friday, the German online magazine Focus caused a national uproar when it reported that two bombs had been planted in the city of Ludwigshafen by a local German-Iraqi youngster who was “very religiously radicalised” and had possibly been “instigated or guided” by an “unknown member” of ISIS.

Later that day, reporters eagerly waited for Ludwigshafen’s mayor, Eva Lohse, to arrive in the town hall. But Lohse could tell them very little. The 12-year-old suspect was in “a safe place” (in the custody of local child protection services—children under the age of 14 cannot be charged with a crime in Germany) where he wouldn’t “pose any danger.” Five minutes later the press conference was over. No further questions were allowed.

The press is buzzing anyway and Berlin has shown itself alarmed: Has ISIS really managed to steer a child into trying to attack his hometown? “It is, of course, an announcement that would shock anyone,” said government spokesman Steffen Seibert.

Meanwhile, the federal prosecutor’s office confirmed on Friday that, yes, it is investigating the discovery of a nail bomb in Ludwigshafen. The device was found near the city’s shopping center on Dec. 5, one day before Saint Nicholas Day, an old-school holiday where going to the mall as a kid in Germany most likely means getting free candy.

But one child clearly had something else on his mind. A passerby alerted the police about a black bag, which the 12-year-old allegedly had dropped in a trash can. Inside the bag was a canning jar with nails taped around it. The jar had been filled with a pyrotechnical mixture made from fireworks and sparklers, which the police later determined to be “flammable, but not capable of exploding.”

In fact, general prosecutor Hubert Ströber declared of this sad little self-crafted device that it was “over the top to describe it as a bomb.”

At Ludwigshafen’s Christmas market, the mood reportedly remains calm and cheerfully kitsch, even though it now turns out a similar device was found deposited there, among the carrousels, fun-fair rides and sausage stalls, on Nov. 26.

“I have difficulties with seeing a 12 year old as a terrorist,” terrorism expert Guido Steinberg told the Mitteldeutsche Zeitung. “It makes sense for when people begin to get interested in politics, at 15 or 16. But how political can you be at 12 years old? It rather raises the question: what is going on in his surroundings? Because it could not have been his idea.”

Indeed. According to the German broadcaster WDR, the boy received instructions for building the bomb via the messenger app Telegram, and this has lead investigators to suspect ISIS involvement.

The precedents for what the French call “remote-controlled terror” are many.

Both 17-year-old Riaz Khan Ahmadzai and 27-year-old Mohammad Daleel were also in contact with alleged ISIS members via online chat, getting advice on how to kill before attempting to commit attacks in July this year.

Daleel had strict instructions from his chat partner to leave his backpack at a music festival in Bavaria, detonate it from a far and film the inferno, before he accidentally blew himself up.

And Ahmadzai’s chat contact sent him a message this summer to suggest he drive a car into a large crowd. Ahmadzai declined. He didn’t have a driver’s license, he wrote. Instead he got on a regional train in Würzburg with an axe and a knife and severely injured three people before being shot dead by the police.

ISIS, which has no qualms about using child soldiers, also seems to have been more than happy to use children and teens as cannon fodder in Germany and in other EU countries like the Netherlands, Austria, and France, reaching out with customized apps and advertising its crimes with what terror expert Peter Neumann called a “pop culture of horror”—teen violence fantasies, complete with flashy pictures and computer games.

German Chancellor Angela Merkel’s chief of staff, Peter Altmaier, said on Friday that legal preconditions have already been improved to respond to the radicalization of minors—but now one will have to see whether further action is needed.

Germany tightened its terror laws in the summer to allow the country’s domestic spy agency to track and collect data on suspects as young as 14 years old. (The previous minimum age was 16.) When first proposed, the measure met with opposition. But that was before 15-year-old Safia S. sank a kitchen knife five centimeters deep into a policeman’s neck at the central train station in Hannover in February this year.

The officer survived, but the wound was life threatening. On her phone, Safia had written chat messages saying that she was in touch with “employees” of the ISIS regime, who had urged her to prepare a “surprise for the infidels.” It was a “martyrdom operation for the terrorist militia ISIS,” according to the German authorities. She is currently on trial for attempted murder, and if convicted she faces a prison sentence of up to 10 years.

We know a little more about Safia than we do about many of the others. Indeed, she had gained a certain fame as the “child star of the Salafists.” She started appearing in YouTube clips with the ginger-haired hate preacher Pierre Vogel when she was only 7 years old.

“Cool outfit,” Vogel compliments her in one of them, when she shows up wearing a headscarf that goes down to her hips. After she sings for the camera, he jokes, “You do the lecture today, and I’ll go home.” In that clip, she was just about 9.

Radical Islam for kids? It’s not the Mickey Mouse Club.