He also served as the Senior Police Advisor in UNAMA from June 2008 to April 2010.[5] He is a former Director General of Rapid Action Battalion, an elite paramilitary unit.
Chowdhury joined U.N. Administrative Mission UNTAES (United Nations Administration in Eastern Slavonia; part of Croatia now) on May 1996 and served the Mission first as Deputy Sector Chief and later Sector Chief of one of the two Sectors of the Mission. Few years later he joined UNMIBH (United Nations Mission in Bosnia Herzegovina), a Monitoring Mission, at Sarajevo on August 1999 and worked in the Mission as Deputy Regional Commander and Regional Commander, Sarajevo IPTF Region among a group of International Civilian Police Officers.[8] In 2001, he as a superintendent of police, he would be promoted to Inspector General in five years superseding many officers senior than him.[9]
Chowdhury worked as Senior Police Advisor, UNAMA (United Nations Assistance Mission in Afghanistan), as a UN Staff member from June 2008 to April 2010. He was elected as the 1st Chair of Senior Police Advisory Group (SPAG) of International Police Coordination Board (IPCB).[5] On completion of the tenure, UNDP Afghanistan contracted him as an International Consultant.
In 2007, after the military-backed government assumed office, fresh investigation into the case was launched on the 2004 Dhaka grenade attack.[16][17]
In July 2008, on completion of investigation CID prosecuted 22 accused and trial began. After Awami League formed government in 2009, prosecution filed a petition to launch further investigation into the incident in June 2009. In July 2011, 23 months after further investigation, CID submitted a supplementary chargesheet where Chowdhury, along with two other former inspectors general, was implicated. He appeared before the Metropolitan Magistrate’s Court and the Judge rejected bail prayer.[16][17]
As Trial of the case resumed, Chowdhury was charged under Section 218 (creating false document) and Section 330 (extorting confession) of Bangladesh Penal Code and granted bail.[18]
Chowdhury was convicted in October 2018 by a Dhaka lower court but High Court stayed the conviction and granted bail in January 2019. [19]
On 1 December 2024, he was acquitted by high court in August 21 grenade attack cases.[20][21]