"Delete ALL pictures and videos of the Islamic State," the Emir warned via WhatsApp.
"Delete your chats."
"Everything that is weapon-like or similar (also bombs) must be immediately disposed of. . . . Sell it, give it away, move it or destroy it."
And then one night last April, officials said, the Emir - a Muslim title for an exalted leader - led two cell members to a Sikh house of worship in this industrial city and hurled the bomb toward its door. A deafening boom rang out. Orange flames lit a mosaic of blood and shattered glass. Inside, victims screamed as the assailants fled.
All three terrorists were 16-year-old boys, according to German police.
"Our children!" cried Neriman Yaman, 37, mother of the Emir, whose first name is Yusuf, in an interview after attending a court hearing for her son. "What is happening to our children?"
"The amount of Islamic State videos and propaganda aimed at children has really jumped in recent months," said Daniel Koehler, director of the German Institute on Radicalization and Deradicalization Studies. "We haven't seen anything quite like this, not on this scale and of this quality. They know that in the West, you don't expect a 10-year-old to be a terror suspect."
Last September, German authorities arrested a 16-year-old Syrian asylum seeker after they discovered he was in contact with an Islamic State handler who was teaching the young man how to build a bomb.
In December, a 12-year-old German Iraqi boy - guided by an Islamic State contact in the Middle East who warmly addressed him as "brother" and groomed the boy via the encrypted messaging app Telegram - built and tried to detonate a bomb near a shopping center in the western German city of Ludwigshafen. The device failed to explode.
The boy had been "headhunted" by the Islamic State, officials said, after searching radical websites online. A 17-year-old accomplice was later arrested in Austria.
Last month, a 15-year-old girl - the daughter of a German convert to Islam and a Moroccan mother - was sentenced to six years in prison for an attack last February on a German police officer in Hanover. She gouged him in the neck with a kitchen knife, causing life-threatening injuries after being befriended and cajoled by an Islamic State instructor via a text messaging service.
All told in Germany, at least 10 minors have been involved in five plots over the past 12 months. In a country where militants disguised as migrants have been blamed for a terrorist plague, most of the minors were homegrown threats born in Germany.
Worse, authorities said, is that the intelligence community is often blind to the threat posed by these teens and preteens.
Officials lack the legal authority to track children the same way they monitor adults, creating what German authorities describe as one of their greatest counterterrorism challenges. Intelligence agencies here have identified at least 120 minors who have become dangerously radicalized - and some of them cannot be intensely monitored because of domestic laws protecting children, officials said.
German law was amended last year to allow for the collection of data on suspects as young as 14. But officials now argue that is not young enough.
"Our service mainly focuses on adults," said Hans-Georg Maassen, head of Germany's domestic intelligence agency. "We are allowed to monitor minors and record them in our databases in exceptional cases only, but they have to be aged 14 or over. Normally people do not expect children to commit terrorist attacks. But they can and are."
He added: "What is really worrying is that people frequently look the other way. They say it's just a phase of adolescence and surely they will grow out of it. Often parents don't really know what their children are doing in their rooms."
Since the start of the Syrian civil war, Europe has grappled with the kind of radicalization that led thousands of its Muslim citizens to travel to the Middle East, often to join the Islamic State. But as Turkey and other nations more actively block the path of foreign fighters to Syria and Iraq, the journey has become harder.
So the targets of radicalized youths are shifting, European intelligence officials said, with terrorist groups either enlisting or inspiring them to attack their homelands. They are employing propaganda tailor-made for youths, including several recent graphic videos showing grammar-school-age children executing prisoners and a newly released computer game, inspired by "Grand Theft Auto," in which users kill enemies under the Islamic State flag.
Islamic State recruiters carefully monitor children who visit their propaganda sites or enter radical chat rooms, meticulously evaluating who may be suitable for cultivation. Typically, they don't immediately attempt to challenge children's relationships with their parents but nudge them toward violence by convincing them that Allah smiles on those who defend the faith. They groom children much the way that pedophiles do - deploying flattery and attention while pretending to be friends, according to people who study the phenomenon.
"They've built a structured recruitment process. They're online, scanning for young adults," Koehler said. "They have stages of [cultivation]. They won't even mention violence until later in their contact, until they've built up trust with these younger recruits."
Often, radicalized minors are also children at risk, either suffering from psychological disorders or living in broken or violent homes. For instance, the 12-year-old detained in December after building his own bomb - which failed to go off only because of a faulty fuse - had been visited frequently by social workers because his father had a history of violence, according to German officials familiar with the case, who spoke on the condition of anonymity to discuss a juvenile. The son of Kurdish Iraqi immigrants, the boy had begun attending a local mosque - alone - that had been previously linked to an Islamist movement.
In the face of terrorist attacks, freedom of religion is being tested in Germany - with even the progressive Chancellor Angela Merkel now calling for an election year ban on the full Muslim covering known as the burqa. A German soccer club recently canceled the contract of one of its Muslim players - Anis Ben-Hatira - after a media uproar over his involvement in a legal Islamic charity that promotes a conservative brand of the faith.
The heightened sense of insulation and persecution among young Muslims, experts said, is only fostering more radicalization.
"Religious extremist propaganda, Salafist propaganda, can only work if it is addressed to an audience that is already marginalized and feeling uncomfortable in society," said Goetz Nordbruch, co-director of Horizon, a German group offering counseling and workshops on Islamophobia in German schools.
"The public discourse is turning against these kids, against Islam," he said. "It is making it harder for them to feel both Muslim and German."
At 6:45 p.m. on April 16, Kuldeep Singh, a 62-year-old cleric and immigrant from the Indian state of Punjab, was passing inside the side door of the Gurudwara Nanaksar Sikh Temple in Essen. Situated on a curved road, the temple is right next door to a mosque.
The temple's glass door was locked. The Sikhs - a faith based on the teachings of Indian gurus - had become concerned for their safety. Young Muslim men from the neighboring mosque had passed by the temple after Friday prayers, spitting at its gate. That Saturday evening, a group of Sikh children gathered for singing classes had gone upstairs so that the adults could pray. Singh was making his way to the altar when he felt a crushing force, searing heat and pain.
A piece of his left foot had been blown off. Shards of glass were lodged in his body. Two wounded worshipers lay near him screaming.
The bleached-out blood from that day still stains the temple's prayer room.
Yaman - the mother of the Emir - is also trying to understand and attending all her son's court hearings.
"I need to. I need to understand what happened to my son," she said.
Yusuf - whose last name is being withheld because he is a minor - grew up the only son of a Turkish meat delivery man and his wife in old coal mining country in west Germany.
"Yusuf was the class clown," said Yaman in an interview in her kitchen. "But his jokes became disruptive behavior. He would go under a table or a desk at school and refuse to come out. We knew he had problems. We tried to get him help."
In 2012, a child psychologist diagnosed him with attention-deficit disorder. Yet the prescribed medication - methylphenidate - made him so lethargic that he could not get out of bed. He complained of violent stomach cramps. "We took him off it after one day," Yaman said.
His behavior nose-dived. He would berate his younger sister and her friends and would throw tantrums.
"He started seeing things - and he asked for God's help," she said. "He said he wanted to know more about his religion."
Yaman's answer was to take him to an event suggested by a friend - a speech by Pierre Vogel, a former boxer and Muslim convert known for spewing radical Islamist rhetoric who called for a public funeral prayer service for Osama bin Laden after he was killed in Pakistan.
"I didn't know," Yaman said, burying her head in her hands. "I had no idea the things [Vogel] said."
But Yusuf was hooked - and he quickly sought out new friends. They were men in Islamic garb from a movement known as True Religion, which for years handed out free Korans from booths in German cities. In November, German authorities outlawed the group, calling it a recruitment network for the Islamic State.
In 2014, the men of True Religion welcomed Yusuf as "a brother."
"He never really had friends - because of his behavior," Yaman said. "But they welcomed him, included him. Gave him respect."
And he absorbed their ideas.
In class, he threatened to break the neck of a Jewish girl - resulting in his expulsion and an order to attend deradicalization classes sponsored by the state intelligence services. For 18 months, to little apparent effect, he received therapy and participated in discussion groups. At the time, his age prevented the authorities from monitoring his communications.
"What we can do is to open the door, but the people themselves have to go through it," said Joerg Rademacher, spokesman for the domestic intelligence branch in the German state of North Rhine-Westphalia.
Yusuf's downward spiral continued. In 2015, he secretly married a burqa-wearing Muslim girl, 15, whom he had met on a website. A radical Muslim cleric presided over the marriage - and chastised Yusuf's parents when they objected.
Using social media, Yusuf also connected with other Muslim boys his age who admired the Islamic State. There is no evidence to date that they had any direct contact with the group, but they collected beheading videos on their phones, praised the militants at school and began to plan their own attack.
In late 2015, the mother of a student at Yusuf's school became alarmed and informed authorities after he allegedly bragged about having a gun. He had also celebrated the November 2015 Paris attacks and warned that students at his school "would die." A search of his family home ensued, but no gun was found.
On Jan. 2, 2016, Yusuf and two other boys built a test bomb at his parents' house, pouring explosive compounds into an emptied fire extinguisher and attaching a fuse. They detonated it at a local park - and showed a video they shot to classmates who reported the incident.
The school summoned Yaman to tell her and also informed the authorities. This time, Yusuf was called in for questioning, but he was not detained. The school did not pursue disciplinary action beyond alerting the police.
"Of course the school has taken action, but we have nothing to do with how the authorities react," said Werner Gallmeister, principal at the St. Michael School that Yusuf attended.
Three months later, Yusuf and his friends attacked the Sikh temple that abutted the mosque where the boys had started worshiping without their parents, officials said. In their texts to one another, recovered by police, they described the temple as a den of infidels.
Major Islamic State attacks involving teenagers in Germany
FEB. 26, 2016: A 15-year-old girl of German-Moroccan origin who was in direct contact with an Islamic State agent stabs a German police officer in the neck with a kitchen knife in Hanover. He survives the attack after undergoing surgery.
APRIL 16, 2016: Three boys, all aged 16, build a homemade bomb and throw it at a Sikh temple, wounding three - one severely - and causing extensive damage. The leader of the group, who goes by the name the Emir, is a German-born son of ethnic Turks.
JULY 18, 2016: A 17-year-old Afghan asylum seeker who professed his allegiance to the Islamic State attacks passengers on a train traveling through southern Germany with a knife and ax, injuring four people, two seriously.
SEPT. 21, 2016: Authorities arrest a 16-year-old Syrian asylum seeker in Cologne after they uncover evidence that he has been in contact with an Islamic State representative who was passing on details for how to build a bomb.
DEC. 5, 2016: A 12-year-old Iraqi-German boy who was in contact with the Islamic State via the messenger service Telegram leaves a homemade bomb that fails to detonate near a shopping mall in Ludwigshafen, authorities say. A 17-year-old accomplice is later arrested in Austria.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)