It was social media chatter that gave him away. Changing his profile picture on the LINE messaging app to a banner pledging "Indonesian support and solidarity for ISIS" probably didn't help.
Had it not been for all that, Gigih Rahmat Dewa's plot to launch a rocket attack on the city-state of Singapore from a nearby Indonesian island might never have been uncovered.
Gigih, 31, and five accomplices were arrested on Batam island on Friday after an investigation that showed how much Indonesia's Islamist militants now rely on social media, including with a Syria-based Islamic State jihadi who allegedly directed them to stage attacks.
It also underlined how militants in the world's most populous Muslim nation, once tight-knit under the Jemaah Islamiah group and internally focused, are splintering into smaller gangs loosely linked to Islamic State with increasingly regional ambitions.
"The men in Batam seem to have been radicalised over social media, specifically using Facebook, rather than directly," said police spokesman Boy Rafli Amar.
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"They have been in communication with Bahrum Naim in Syria.
"It looks like he sent funds and instructions to them," he added, referring to the suspected mastermind of the Singapore plot who left Indonesia in 2015 to join the frontlines of Islamic State.
Multi-ethnic Singapore, sandwiched between two large, Muslim-majority nations, has never seen a successful attack by Islamist militants. But the government of the wealthy island state has said repeatedly it is only a matter of time.
According to police, Gigih and his group had been instructed by their mentor in Syria to fire a rocket at Singapore's Marina Bay, a glitzy downtown waterfront area that hosts a Formula One Grand Prix and is home to a casino resort and office blocks.
Residents of Batam, 15 kilometres south of Singapore, said they were dismayed to learn that the six local men, five of whom were local factory workers, were extremists.
Gigih, his wife and infant daughter lived in a modest one-storey house in a row of many just like it. His Facebook account showed that he enjoyed cycling and hiking.
"We are shocked that a completely ordinary person like him can be like that, can be suspected of being involved in radicalism," said neighbour Rubiyati, who goes by one name.
Monalisa, a 23-year-old who attended Batam's state polytechnic institute at the same time as Gigih, described the IT student she knew until 2014 as a normal guy who was "positive, cheerful, humble and friendly with everyone".
She was, however, surprised in March of that year when Gigih changed his LINE group chat picture to a photo of a group of people holding up an Islamic State banner.
There was no preaching by hardline Islamists on campus and so it is unlikely he was radicalised there, she said.
"But what people do off campus or online is another matter."
