Rubaiyat Sharmin Rumpa went to the Ayesha Complex, the building in front of which her body was found on Wednesday, to meet one of her school friends.
She left the building after talking to her friend, but police are yet to find out the turn of events that occurred immediately before her death.
Police sources said, around 4pm on that day, Rumpa went to a place near Stamford University campus to meet her former boyfriend Abdur Rahman Saikat. Rumpa tried to resume their affair, but Saikat refused her.
Rumpa became angry after she failed to convince Saikat, and left the place.
From there she went to her home in Siddheswari area and from there she went to her friend's flat in the Ayesha Complex.
After visiting her friend, she went to tutor a student and returned around 6:30pm. But instead of entering her home, she called a cousin to bring her a pair of slippers in front of the building.
When her cousin came, Rumpa gave the cousin her bag to take home.
The Detective Branch (DB) of police is investigating what happened from that point on till her death.
Rumpa's father Rokon Uddin, a police officer posted in Habiganj, filed a case over the incident against unidentified attackers on Thursday. The case was moved to the Detective Branch from the Ramna Police station on Saturday.
On the same day, the DB detained Saikat from an area in the capital.
DB sources said, after primary interrogation they got some information from Saikat.
In the appeal to take Saikat in remand, police expressed suspicion that Rumpa was thrown off from the rooftop of the Ayesha Complex by Saikat and his associates.
Akhtaruzzaman Ilias, inspector of the Detective Branch, said, on Sunday Police produced Saikat before a Dhaka Court with 7-day remand plea for his alleged involvement in Rumpa's murder.
The court then placed Saikat on a 4-day remand.