The hand-drawn sketches of the interior of the bank were found when police raided a house in Tongi’s Aushparha.
The police were aware of the cards of the suspects they questioned about the incident.
One of the sketches matches the design of the first floor of the bank, Dhaka District Police Deputy Superintendent Nazmul Hasan Firoz told bdnews24.com.
“Circles” denote people, “Toy” means toilet and “MG” was used to mark the bank manager’s room. Entry and exit routes have also been mapped out.
Police are working to decipher the other sketch, ASP Nazmul said. “This may lead us to more information.”
A gang of thieves attacked the Bangladesh Commerce Bank branch at the Kathgorha Bazaar in Ashulia on April 21. They detonated bombs before shooting and killing three people, including the bank manager and the security guard.
The men, fleeing after looting money, were arrested by residents outside. Four died when thieves opened fire and detonated explosives.
Two thieves fell from their getaway motorcycle after locals chased them. One was beaten to death by a mob and the other died two days later in a hospital.
Police, after analyzing the nature of the heist, suspected extremists were implicated.
Several of the 11 suspects arrested are members of a banned extremist group – the Ansarullah Bangla team.
On Saturday evening, the police arrested a certain Mahfuzul Islam Shamim, a senior leader of Ansarullah. Police said he was the “operation commander” of the attack.
Shamim planned the heist at his rented house in Aushparha and led the attack, ASP Nazmul said.
Another suspected thief, Al Amin Hossain, while testifying in court under section 164, said Shamim led the attack.
JMB in Ansarullah
Two years ago, police raided a training camp in Bogra by the banned activist group Jama’atul Mujahideen Bangladesh (JMB).
Shamim, then a member of the JMB, had managed to escape with weapons, police said.
Detectives say Shamim and several of his supporters joined the Ansarullah Bangla team due to a rivalry with JMB Salauddin’s agent.
Salauddin is a death row inmate who was one of three JMB radicals freed from a prison van attacked in Trishal de Mymensingh last year.
“Shamim was also involved in the incident when one person was killed and Tk500,000 of bKash money diverted from the Gazipur Boardbazar on March 10,” ASP Nazmul said.
He had never been arrested before, but confessed to murders and other crimes during his examination-in-chief, police said.
Shamim confessed to being involved in several crimes when he was brought to justice on Sunday.
“Ashulia’s heist was planned in advance,” ASP Nazmul said.
“The members of the Ansarullah Bangla team did this to raise funds and scare the public.”
Police monitored an area of Aushparha for two days after being informed. A one-story house was quickly identified as the thieves’ “hiding place”, where the two sketches were found.
Shamim, the “operation manager,” had rented the house four months before the theft and was living there with his wife and a few associates, ASP Nazmul said.
The agents sold “lighters, torches and so-called energy drugs”, while Shamim’s wife was left home alone. They put the money in the group’s funds and spent the rest on themselves.
“Each of them carried a hand bomb and a knife during the robbery. Two pistols and a two-barrel rifle were also used. The weapons appeared to have been made in China, ”ASP said.
“The police found knives, lead powder and similar tools for measuring chemicals used to make bombs.”
Shamim was asked why the victims were killed in this way during the robbery. He told police he “hadn’t done it for himself.”
“He replied without concern, ‘Sir, I am with the organization to please Allah, not for myself.”
“He bowed his head when asked if the Holy Quran contained such instructions.”