Tamim Ahmed Chowdhury was the man on whose head Bangladesh police placed a Taka 2 million (20 lakh) bounty, nearly one month after the July 1 terrorist attack in Gulshan, as one of the masterminds of the attacks.

Previously he was known for some time to the international media as the local coordinator for Islamic State (IS) in Bangladesh, although police said that he was a high-ranking member of a faction of the local militant group called the ‘New JMB.’

Tamim lived in Windsor, Canada for much of his life, from where he returned to Bangladesh on October 5, 2013, reports UNB.

Investigators said Tamim was hiding out in the northern districts of the country conducting a number of killing missions since his return. Having gained sufficient confidence he finally executed both the Gulshan and Sholakia attacks, investigators said.

One of the captured militants from a raid in Kalyanpur in the capital, Rakibul Hasan alias Rigan, reportedly confessed that a ‘Big Brother’ used to come to their apartment to provide funds and give instructions. Police say Tamim was one of these brothers.

Monirul Islam, chief of counter-terrorism and transnational crime unit, told reporters that they have information that Tamim was in Dhaka during the Kalyanpur raid. Inspector General of police AKM Shahidul Hoque said that Tamim is the mastermind behind the Gulshan attack.

Tamim was the grandson of Abdul Majid Chowdhury of Sadimapur in Borogram Union, Sylhet.

Abdul Majid was a member of the infamous razakar committee known as the ‘Peace Committee’ during the liberation war, according to locals. Tamim’s father Shafiq Ahmed Chowdhury was a crew member in a ship. He moved to Canada with his family after the liberation war.

Chowdhury was profiled and interviewed in April in an issue of Dabiq, the slick English-language magazine from IS.  The Dabiq article called Shaykh Abu Ibrahim al-Hanif the ‘Amir of the Khilafah’s Soldiers in Bengal.’ Al-Hanif was actually Chowdhury, a quiet former resident of Southern Ontario who, according to those who remember him, was hardly the fearless commander that he’s made out to be in the magazine.

The connection was first made by Zayadul Ahsan Pintu, a former journalist and expert on militancy, in the Daily Star, where he said that that al-Hanif is simply the nom du guerre of the Bangladeshi-Canadian.

The Canadian researcher Amarnath Amarisingham, a Fellow at The George Washington University’s Program on Extremism, and co-director of a study of Western foreign fighters at the University of Waterloo in Ontario, Canada, has been trying to pin down Tamim Chowdhury and find out about the life that led him into IS, for quite some time. According to him:

He was born on July 25, 1986. It is not clear yet if he was born in Canada or Bangladesh (probably the latter), but he is indeed a Canadian citizen. He likely attended J.L. Forster Secondary School in Windsor. He competed for the school in a variety of track and field activities in 2004.

He graduated from the University of Windsor in Spring 2011, with an Honors in Chemistry, but probably majored/minored in other fields as well. Some time after graduating from Windsor, he traveled to Calgary. It is unclear whether he moved to Calgary, or simply traveled back and forth several times. The latter seems more likely since those Amarisingham spoke with in Calgary only remember him intermittently. He seems to have stayed low-key perhaps, and did not mix too closely with the Muslim community there.

One source says he remembers Tamim hanging out with Damian Clairmont at the 8th and 8th musallah, where Damian, Salman Ashrafi, Collin and Gregory Gordon, another individual named Waseem (last name unknown, but not Ahmad Waseem), and a few others held a private study circle. According to friends of theirs, Damian was likely the one who took a leadership role over the group, but it could be that Tamim was equally influential.

The same source says that Tamim almost certainly went to Syria, either directly from Calgary or from Windsor, ‘probably’ in late 2012. Another source claims he saw Tamim hanging around the University of Calgary in 2013. This is further complicated by the fact that religious leaders in Windsor say they asked Tamim not to engage with youth at the mosques, clearly worried that he was potentially radicalizing them. This was possibly some time in 2013 as well. As such, details on when exactly he travelled to Syria are still murky.

From Syria, Tamim likely found his way to Bangladesh, perhaps even on direct orders from ISIS leadership.

In the Dabiq interview, al-Hanif declared with pride that the emergence of ISIS militants in Bangladesh has ‘terrified the kuffar [unbelievers] in the region in general and in particular the atheists and secularists who mock Islam.’

Not much is known about Chowdhury’s life in Canada. Amarnath Amarasingham said he had heard of Chowdhury from a community activist in Windsor, who mentioned he may be travelling to Syria several years ago. While Amarasingam hasn’t been able to confirm whether or not Chowdhury did, in fact, end up in Syria, his name later popped up in an IS study group website as someone who was active in Bangladesh.

‘Not many people knew him. The few people who knew him said he just kind of hung around the mosque in Windsor, was a skinny guy, was a shy kid,’ said Amarasingam to VICE News. His age and immigration history aren’t known.

The researcher suspects Chowdhury came onto law enforcement’s radar because he knew Ahmed Waseem and Mohammed Al Shaer — two men who allegedly left Windsor to join ISIS in Syria in 2013 — and that he left Canada ‘shortly after harassment from the police,’ who were questioning Waseem’s known associates at the time.