Detectives have arrested a “mastermind” behind the killing of publisher Faisal Arefin Dipan and the attack on another publisher, Ahmedur Rashid Tutul, last year.

During his primary interrogation, the arrestee, Abdus Sabur alias Samad alias Sujon alias Raju alias Saad, 23, admitted that he motivated and provided training to the Ansarullah Bangla Team (ABT) members who attacked the publishers with machetes, claimed police.

Law enforcers also suspect that Sabur, arrested at Tongi Railway Station in Gazipur on Saturday, was also directly involved in the murder of writer and blogger Avijit Roy on Dhaka University campus on February 26, last year.

Meanwhile, a Dhaka court yesterday placed him on a six-day remand in the case filed over an attempt to kill Tutul.

Interrogators have already gleaned some “important information” about Avijit murder from Sabur, Monirul Islam, chief of the Counter Terrorism and Transnational Crime unit of Dhaka Metropolitan Police, said at a press briefing at the DMP media centre yesterday.

Sabur, a madrasa student, used his knowledge of Arabic to disseminate distorted religious interpretations among new recruits at the training camps of the banned militant outfit ABT, he said.

“Through the distorted religious views, he convinced the attackers that killing the publishers would not be a sin,” he added.

In what appeared to be synchronised attacks on publishers of Avijit, assailants hacked to death Dipan of Jagriti Prokashani and critically injured Shuddhoswar's Ahmedur Rashid Tutul on October 31 last year.

Detectives on June 15 this year arrested a suspect, Sumon Hossain Patwari alias Sakib alias Shihab alias Saiful, 20, who directly took part in the attack on Tutul.

In August 23, detectives arrested Moinul Hasan Shamim alias Sifat, who was identified as a key plotter of Dipan murder.

Investigating the incidents and on information given by the two arrestees, detectives identified and arrested Sabur, who is known among "his fellow militants" by different names, said the police official.

Razib al Masud, additional deputy commissioner of detective branch (South) of the DMP, told The Daily Star that Sabur, Shihab and Sifat had taken bomb-making training at the militant den in Mohammadpur which was later busted by police on February 19 this year.

Monirul said the DMP had earlier announced a Tk 2 lakh bounty on Sabur, who is one of the four leaders of the ABT's military wing.

“The foot soldiers, who were present at the crime scenes, acted as toys operated by remote controls,” he said.

He claimed that Sabur was one of the planners who was not present at the scenes but played a key role in preparing the attackers.

He said police were taking the planners more seriously as they could recruit other militants.

Because of his intelligence, Sabur came under the attention of a “Boro Bhai” (big brother) while studying at a madrasa in the capital's Jatrabari area.

At first, the recruiter told him to be attentive in his studies and later started to indoctrinate him.

At one point, the “Boro Bhai” asked him to leave his home and take shelter in a hideout, Monirul said. Sabur left his home in Comilla at the end of 2014.

The recruiter also arranged a meeting between Sabur and sacked army major Ziaul Haque, the operational commander of ABT, said a DB official preferring anonymity.

Sabur is from a village in Dhalia union under Nangalkot upazila of Comilla. In the remand prayer, police mentioned that he lived in Cherag Ali area of Tongi.

HOW THEY OPERATE

When militants go to “sleeper cells” or “safe houses”, their leaders initially do not tell them about their targets, said Monirul.

Apart from being injected with the misinterpretation of religion, the militants also receive training on weapons, track their targets using “digital surveillance” and avoid being detected.

“Before the end of the training, the foot soldiers are told about their targets, and the so-called reasons why the targets should be killed. They are told that the blood of their targets is worthless and killing them is faraz [compulsory],” he said.

Those who are not that intelligent are selected as the foot soldiers while the smarter ones become the planners.

The recruiters target impressionable young men and build personal relationship with them, sometimes by talking about religion and sometimes by talking about their personal lives, said Monirul.

“The recruiters detect the vulnerabilities of their recruits first. For example, when they see that a boy is facing difficulties in mingling with others, they approach him and become his friend,” he said.

While spreading misleading information about religion, the recruiters identify the smarter ones from the others and decide their future roles.