Major (retd) Sinha was the operation officer of Border Guard Bangladesh in Teknaf and played an active role in the anti-narcotics operations.
Lt Col Md Faisal Hasan Khan, commanding officer of BGB Battalion-2 in Teknaf, said Sinha served as acting operations officer at Teknaf BGB from October 2017 to January 2018.
"He was a smart and brilliant officer. So, definitely he played important role in the drives against narcotics," he added.
Despite repeated attempts, no Rab officer could be contacted to comment on whether Sinha's posting in Teknaf BGB had any links to his murder, which his sister claimed was "a planned and cold-blooded murder" in the case she filed.
Meanwhile, Rab yesterday did not take any of the 10 accused arrested so far in the Major (retd) Sinha murder case in their custody from jail to interrogate them.
Asked, Rab said the reason they postponed the interrogation was that they had stumbled upon some additional information about the Sinha murder on social media. "We have to verify those informations before we go into questioning," Rab said.
It added that they would interrogate Shipra Debnath and Shahadul Islam Sefat, witnesses to the Sinha killing, on Sunday and that too is when they will bring in the 10 accused on remand.
"We don't know if Sinha's recruitment in the BGB was a reason for the murder. We are investigating every possible angle," a Rab official said.
A Rab team went to Cox's Bazar jail in several vehicles around 11:00am yesterday, but they returned after around 15 minutes without taking any of the accused with them, said Jail Superintendent Mokammel Hossain.
The seven accused policemen are former officer-in-charge of Teknaf Police Station Pradeep Kumar Das, Inspector Liaqat Ali, Sub-Inspector Nandadulal Rakhshit, ASI Liton Mia and constables Safanur Karim, Kamal Hossain and Abdullah Al Mamum.
The three others accused are Nurul Amin, Nizam Uddin and Md Ayash, who were made witnesses in the cases filed by SI Nandadulal following the shooting death of Maj (Retd) Sinha Md Rashed Khan.
Sinha, 36, had been making travel documentaries for a YouTube channel called "Just Go". On the fateful night, he was returning to Cox's Bazar from Teknaf with Sefat.
His car was stopped at Shaplapur on Marine Drive.
Police claimed they tried to search the vehicle, and Sinha aimed his pistol at them prompting them to shoot back in self-defence. They also claimed they seized drugs from the vehicle.
However, witnesses gave a different account of the incident. They said Sinha got down from his car, put his hands over his head and then the inspector shot him.
Meanwhile, the Criminal Investigation Department of police (CID) has been assigned to investigate other criminal charges against Pradeep and 29 others.
On the other hand, a Cox's Bazar court yesterday dismissed a complaint filed against arrested Pradeep Kumar Das, who earlier served as the OC of Moheshkhali Police Station, and 29 others, for killing one Abdus Sattar in an "encounter" with police in 2017.
The court also asked a CID official, equivalent to the rank of additional superintendent, to investigate the complaint, reports our Cox's Bazar correspondent.
Senior Judicial Magistrate Mohammad Abbas Uddin yesterday passed the order after Hamida Akhtar, wife of slain Abdus Sattar, filed the complaint against the former OC and 29 others at the court yesterday.
Plaintiff Hamida, in her complaint, said that Pradeep picked up her husband from their house in Majherpara village under Moheshkhali upazila on February 14, 2017, and killed him in "a crossfire".
Claiming that her husband was innocent, she said police staged a drama of crossfire in the interest of one Ferdous, a ringleader of a local armed group.
The plaintiff's lawyer Shahidul Islam said his client filed a petition to the High Court seeking justice and the HC asked the superintendent of police in Cox's Bazar to take necessary measures in this connection.