The dead was identified as the 33-year-old Mustafa Kamal. He was named in at least 11 cases with the police, Ullapara Police OC Dewan Kaushik Ahmed told bdnews24.com.
Police arrested four others with 21 bottles of the cough syrup Phensedyl and 80 yaba tablets after the incident at the Upazila's Ghoshgati area, the OC added.
The detainees are Sajib Kumar Saha alias Ganesh, 24, Sonjoy Chandra Saha, 19, Sunny Ahmed, 35, and Selim Reza, 24.
Informed of a drug trade taking place in the area, a police team launched a raid early on Saturday morning, said OC Dewan.
"The drug dealers opened fire when the police arrived at the scene. The police retaliated and at one point, drug peddler Mustafa was shot in the crossfire."
"The armed assailants fled the scene shortly afterwards," he added.