The son of the deceased woman filed the case with Raipur Police Station (PS) in connection with the murders.
The alleged attacker, identified as Antar Majumder, 28, was later beaten to death by an angry mob.
No case has yet been filed over the death of Antar, although police said preparations are underway to do so.
Earlier, a woman and her three daughters were hacked to death at their rented house in a busy area of the municipal town on Thursday.
The deceased were identified as Shahinur Begum, 38, and her daughters Sayma Akter, 21, Nafisa Akter Ikra, 17, and Fatema Akter Shifa, 10.
The bodies of the four deceased were handed over to their family members after autopsies were conducted at Lakshmipur Sadar Hospital. The family said the bodies would be taken to their ancestral home for burial.
According to police and eyewitnesses, the attack took place on Thursday morning at a ground-floor apartment of a five-storey building owned by Amir Hossain Master on Dhanhata Riverbank Road in Raipur Municipality.
Hearing their screams, a neighbour, Afroza Begum Rani, reportedly spotted a man inside the apartment through a window and locked the building’s main gate from outside, trapping the suspect inside.
After she alerted nearby residents, locals entered the apartment and found the victims lying in pools of blood on the floor.
The suspect allegedly climbed to the roof and attempted to escape through a neighbouring building but was caught by locals and mercilessly beaten up. He later succumbed to his injuries.
Police said Antar had lived as a tenant on the fifth floor of the same building for about one and a half years before moving out around eight months back.
Investigators are examining whether the attack was motivated by robbery, as the suspect reportedly knew that tenants deposited rent payments with Shahinur and that she possessed some gold ornaments.
Officer-in-Charge (OC) of Raipur PS Shahin Mia said the complaint filed by the victim woman’s son was being processed as a formal case.
“District Police and Detective Branch personnel in plain clothes are working extensively in the field. A five-member investigation committee has also been formed to investigate the matter,” the OC added.
Lakshmipur Sadar Hospital Residential Medical Officer (RMO) Dr Arup Pal said autopsies had been completed on the four victims.
“Each of them sustained sharp-weapon injuries to the head, chest, hands and other parts of the body,” he said.
