On a Friday in early November 2025, the quiet of a Jakarta school mosque was shattered by a series of explosions. Ninety-six people were injured in the blasts, which scattered shoes, prayer mats, and shards of glass across the mosque courtyard. The attack, carried out during Friday prayers, sent shockwaves through Indonesia, a nation with little history of homegrown white supremacist violence. The suspect? A 17-year-old student, now at the center of a troubling investigation into youth radicalization and the dark influence of online communities.
According to Reuters, police say the teenager acted alone, constructing seven crude bombs in his family’s modest North Jakarta home. Four of those bombs detonated as worshippers lined up for prayers; three failed to explode. The student, whose identity has not been released due to Indonesia’s juvenile crime regulations, is now recovering in hospital after an apparent suicide device meant to end his own life failed to detonate properly.
The story that has emerged is one of deep isolation, technological savvy, and the dangerous appeal of extremist online spaces. Investigators, combing through the suspect’s internet history and raiding his home, discovered a 42-page diary, written mostly in English and titled "Diary Reb." Jakarta police spokesperson Reonald Simanjuntak told Reuters that the diary offered a window into the teen’s state of mind. "He wanted to be recognised by members of the online community … because he feels lonely," Simanjuntak explained. The diary contained not only the suspect’s personal struggles and feelings of alienation, but also detailed attack plans, sketches of the mosque and school layout, and the handwritten date: November 7, the day of the attack.
The student’s relatives painted a portrait of a withdrawn young man. Rundiati, a 53-year-old relative who lived with him, described how he spent most of his time alone in his room, emerging only to eat. "He was always on his laptop in his room," she recalled, noting that the boy had become even more withdrawn after his parents divorced and his mother remarried. Police say he had no outlet for his emotions, either with family or friends.
Yet, in the online world, he found a sense of belonging—albeit a sinister one. The teenager was active in an international Telegram channel where members glorified notorious acts of violence, including the 2019 Christchurch mosque massacre in New Zealand and the 1999 Columbine High School shootings in the United States. Police believe the suspect drew inspiration from these events, which have no historical precedent in Indonesia’s predominantly Muslim society.
Telegram, for its part, says it forbids the promotion of violence on its platform. "Moderators use AI tools to monitor public areas of the platform and remove millions of pieces of harmful content each day, including material that promotes violence," Telegram spokesperson Remi Vaughn told Reuters. However, the suspect’s involvement in such a group highlights the ongoing challenge of policing encrypted and semi-private online spaces.
Police revealed that the student built his bombs by following instructions from YouTube videos. He was able to buy materials such as potassium chloride and nails from online marketplaces without triggering any red flags—a security lapse that authorities say will be closely investigated. To avoid suspicion at home, he reportedly told his father that the chemicals and toy guns he ordered online were for cosplay, a popular hobby among Indonesian youth.
In his diary, the teenager wrote not only about his plans for the attack but also about his own psychological pain. Police say he referenced past trauma and expressed a desire to end his life while also harming others. The attack was carefully timed and planned to maximize casualties, according to Simanjuntak. Choosing Friday prayers at the school mosque meant the largest possible number of victims would be present.
Indonesia, the world’s fourth most populous country, has a rapidly growing youth population. About two-thirds of its social media users are members of Generation Z. The government has taken steps in recent years to limit access to social media for younger users, but the case of the Jakarta bomber underscores the difficulty of keeping up with the evolving tactics of online radicalization.
In a separate but related incident, Indonesian police announced the arrest of five suspects accused of recruiting 110 children aged 10 to 18 into terrorist networks. While these arrests were not directly linked to the mosque attack, officials said both cases point to the urgent risks posed by the online radicalization of young people. The fact that a teenager could plan and execute such an attack, apparently without the knowledge or support of any established group, has alarmed both authorities and the wider public.
As the investigation continues, questions remain about how the suspect acquired his bomb-making materials without detection and what more can be done to prevent similar attacks in the future. Police plan to question the suspect soon, but his legal fate is still uncertain. Before any formal charges are filed, Indonesia’s parole and probation office will assess whether the teenager is fit to stand trial and what form any legal proceedings should take. Simanjuntak noted that the office will also decide whether the boy should be turned over to the state or returned to his parents, though no timeline has been provided.
The broader challenge of curbing online extremism looms large. The press office of Google, which owns YouTube, did not immediately respond to requests for comment about the suspect’s use of the platform to learn bomb-making techniques. Meanwhile, Telegram’s efforts to remove violent content are ongoing, but the existence of such channels—and their ability to inspire real-world violence—remains a pressing concern for law enforcement worldwide.
For now, the community in North Jakarta is left to grapple with the aftermath of the attack. Military personnel have been stationed near the school complex, and residents gather in small groups, still processing the events of November 7. The case has prompted soul-searching about the pressures faced by Indonesia’s youth, the reach of online radicalization, and the vulnerabilities in the country’s security apparatus.
As authorities sift through evidence and policymakers debate next steps, the story of the Jakarta school mosque bombing serves as a stark reminder: even in places with no tradition of such violence, the toxic influence of global extremist networks can take root in the most unexpected of places—and with devastating consequences.