The traders were returning to their neighbourhood after buying vegetables from the wholesale market in Manikganj’s Jaagir.
Arrested police officer Md Asaduzzaman is directly involved in gunrunning, RAB officials claimed.
The two other arrestees are Saiful Islam and Mahmudul Islam.
The trio was detained during a raid on an under-construction house at Uttara sector-6 on Wednesday afternoon, RAB-1 Commander Tuhin Mohammad Masud told bdnews24.com.