They are known as Bhola-Khaleque gang.
Using the name of a ruling party leader of Bhola, they have established a reign of extortion in the slum areas of Moghbazar and Malibagh, locals allege.
Abdul Khaleque, the gang leader, and his close aides Shah Alam, Jahangir, Nuru and Mazid are from Bhola too. Police never dare touch them though their criminal activities, including drug peddling, are no secret.
According to a detective, the underworld in the slum areas is controlled by people mostly from the southern district.
Kailla Babu, a suspect in Thursday night's Moghbazar triple-murder, and Shamim alias Kala Chan, whose sister Ranu Akhter Brishti was among the three victims, were active members of Bhola-Khaleque gang.
The two used to extort money from owners of under-construction buildings and traders of Moghbazar and Malibagh slum areas in the capital.
Locals added that the relations between the two started to worsen a year ago when Chan's uncle Rony sold his four rooms of a six-room tin-roofed house to Chan and Ranu.
Babu had been demanding Tk 3 lakh from the siblings in exchange for allowing them to live in the house, allegedly built occupying government land at Sonalibagh.
Failed to realise the amount, Babu and his cohorts shot dead Ranu, family members claim.
Hridoy, another brother of Ranu, was injured while his friends -- Mohammad Munna and Billal Hossain -- were also killed in the attack. The injured is undergoing treatment at Dhaka Medical College Hospital.
According to police, Babu is a hitman and an accused in two murder cases -- one for killing an Ansar member in Moghbazar in March and another for killing Mobarak Ali, father-in-law of Tuba Group Managing Director Delwar Hossain.
He has been staying out of his Moghbazar home for several years.
Contacted, Khaleque said he has no link to any crime and he did not know Kailla Babu. Identifying himself as a leader of ward-36 Jubo League in Moghbazar, he however said Kala Chan is involved with the organisation.
Assistant Commissioner Shiblee Noman of Dhaka Metropolitan Police (Ramna zone) said, "We know Abdul Khaleque as a man of bad repute. I asked the OC [of Ramna Police Station] not to allow Khaleque into the police station."
He added they picked up two women -- neighbours of Ranu and relatives of Kailla Babu -- for interrogation.
Last night, Chan filed a case in connection with the triple-murder with Ramna Police Station, accusing fifteen people, including Babu.