The bullied Finnish teenager who became an Isis social media kingpin – and then got out

A year ago, at the height of Isis's social media rampage, a shy, 19-year-old Finnish convert to Islam, who had never even been to the Middle East, was one of the terror group's most devastating propaganda weapons.

Abdullah was prolific. His Mujaahid4Life Twitter account, with close to 11,000 followers, was the second most-followed English pro-Isis account after Shami Witness. He tweeted graphic photos and videos, snippets from religious texts, battlefield updates and violent, hateful propaganda. At the time, Abdullah told Newsweek he was "a diplomat for Isis". He was a virtual jihadi, an advocate for violence in the name of Islam. Today, he's just another awkward adolescent tweeting from behind a mess of food wrappers in a darkened flat in a mid-sized European city.

Abdullah has recanted his support for Isis and says he wants to help other acolytes do the same. He's one of few people to renounce his violent extremism, and, to those combating online jihadism, he brings a rare view from inside its echo-chamber. "When I was in that Isis bubble, I was thinking so emotionally," he says. "When you're younger you don't have the intellectual capabilities to process it. It was an obsession, just blind devotion."

It's an alarmingly short path from hip-hop fan to radical jihadist: "The internet is such a huge part of recruiting these days, it's not even funny," says Abdullah. "It's like, 99% online. For the kids who do this, it's easy to conceal it." Abdullah, raised in an atheist home, had become curious about religion as he wrestled with teenage questions of identity and belonging. He found Islam and felt it made sense of the world. He converted in November 2012, declaring the Shahada, or testimony of faith, alone in his bedroom.

His mother, who asked not to be named to protect her family's privacy, watched as her intelligent, emotionally fragile son become increasingly absorbed in his new faith. "At first, I thought it would be a passing thing, like many other phases before. He was 17 at the time and had no friends and no social life," she recalls. "Knowing my son, I wasn't worried that he would leave the country to join the fighting. My worry was the connections he was making online and how much he was sharing about his 'real' identity on the internet."

Abdullah spent most of his time online, looking for people who shared his desire to follow what he calls "a more pure understanding of Islam". He connected with Jabhat al-Nusra supporters, who steered him to Inspire, the al-Qaida franchise's English-language magazine. "Inspire really affected me. And that, coupled with the oppression of Muslims I saw on the news, had an emotional effect," he says.

By the spring of 2013, Abdullah was tweeting support for Jabhat al-Nusra. By summer, he was doing press-ups and crunches, packing a bag and planning to go and fight in Syria. Agents from Finland's security services, Supo, were soon at his door: they had noticed his activity online and asked him not to go. Rumbled, Abdullah continued to support Nusra's jihad from afar.

When Nusra and the upstart Islamic State of Syria and al-Sham (Isis) came head to head in late summer 2014, Abdullah felt he couldn't remain neutral; he had to choose a side. He chose Isis, and waded deeper into an online community built around sharing what he now describes as a "cherry-picked" interpretation of Islam.

As his profile rose, Abdullah knitted deeper into this community. For someone who had been bullied viciously in primary school, the sense of being part of something important resonated. "What drew me in was actually doing something, explaining stuff. You disseminate that propaganda, so it makes you feel part of something bigger. Especially after Isis declared the caliphate," he says.

Charlie Winter, a researcher with the Quilliam Foundation think tank, says this is a common feeling among online propagandists: "It's an easy way to take part in jihad without putting themselves at risk." In Finland, disseminating propaganda the way Abdullah did isn't illegal unless there is an overt recruitment element – something Abdullah says he carefully avoided.

According to Supo, the Finnish Security Intelligence Service, a little more than 60 Finns have travelled to Syria to fight, and, already, a third of them have returned. Supo's Tuomas Portaankorva says: "The possible threat from the returnees is our priority at the moment. Web monitoring is only one line of our work. What we see online is mostly connected to those who have travelled, or are about to, or are returning."

Although Supo reached Abdullah before he could go, there's no telling how many of the foreign fighters who continue to stream into Syria were inspired by him, or others like him. The agency won't comment on individual cases, but Portaankorva admits that the issue of how to handle online supporters is a thorny one. "Without these individuals, there would definitely be, in general, fewer travellers," he says.

Abdullah began to question Isis when the group killed the British aid worker Alan Henning in October 2014. He looked to classic scholarship for justification for the violence but couldn't find any. He tried to start discussions around theological texts, but no one wanted to talk: "It's all see no evil, hear no evil."

By the end of the year, Twitter was shutting down pro-Isis accounts and Abdullah wasn't interested in the daily scramble to create a new account and propagate a worldview to which he no longer subscribed: "When I went back to what Islam teaches, I saw no justification for these things. My message to young people is to go back to Islamic roots, stop living in the bubble. As Muslims we should go back to the religion itself, not what anyone claims." Abdullah's experience points to a need to counter Isis on an ideological level – one that feels authentic to participants and has the theological authority to give them something to hold onto as they reject extremism.

After months out of the social media loop, Abdullah has returned to Twitter as an anti-extremist to convince would-be jihadis to reconsider. Going back hasn't been easy. The vitriol has been immense – and familiar. "To go from someone who is making takfir on people to someone who has takfir made on him..." Abdullah sighs. "I didn't think it was going to be this harsh. There's a weird, dark irony to it."