Sitting across a table with a detainee from the militant Islamic group Jemaah Islamiah (JI) around 2003, psychologist Jansen Ang was puzzled when the man confessed to having taken archery courses.
Why archery, and how relevant was it in today's terror attacks, he asked.
The prisoner replied: A true warrior is one who knows how to shoot while riding horseback.
To many this might sound archaic, but to the JI members, it was possible because they had been brainwashed to believe they were warriors in a holy war against enemies of Islam.
"It was the JI's way of believing in an ideology and sustaining their belief in it," says Mr Ang, 43, senior principal psychologist with the Singapore Police Force.
The JI clandestine network was smashed in two security clampdowns in 2001 and 2002. Since that first arrest, more than 60 have been detained for their involvement in terrorism-related activities. Of these, more than two-thirds have been released.
All 64 men locked up were dead serious about executing their cruel plot to kill many in Singapore, according to the 2003 government White Paper on the JI arrests and the threat of terrorism.
Internal Security Department (ISD) officers found in their haul topographical maps with marked-out areas which were "kill zones".
Hunting knives for jungle survival and bomb-making devices were also confiscated.
The JI had planned to blow up water pipes, Changi Airport, foreign embassies and companies.
To understand what motivated JI members, the ISD approached psychologists in the public service to interview 31 men nabbed in 2001 and 2002.
The ISD was keen to know why ordinary men with no criminal backgrounds were prepared to carry out horrific criminal acts in the name of religion.
Among the four senior psychologists approached was Mr Ang. Their work started in 2002 and took four years to complete.
"Before meeting the detainees, we had long sessions on the approaches to use. Should we challenge them or let them talk freely?" he recalls.
Since joining the Police Psychological Unit in 1995, Mr Ang has worked in the police crisis negotiation unit and the police psychological unit which counselled cops. He is now a deputy director at the Home Team Behavioural Sciences Centre.
He graduated in 1995 with an honours degree in social science in psychology from the National University of Singapore. In 2001, he obtained his master's of science in forensic psychology from the University of Surrey, Britain.
"When I heard the news of the arrests, I kept asking myself 'how can this happen in Singapore and what is going on in the minds of these people'.
"We took psychological snapshots of the detainees' minds, asking the 'who, how and why' questions," he says.
The detainees were motivated by the power of the deviant JI ideology, which was linked to Al-Qaeda's plans to destroy the United States and its allies, and to establish pan-Islamic caliphates.
Another finding, he says, was the family connections among JI members. Brothers and bro-thers-in-law joined and remained in JI because of kinship ties.