It came after the law-enforcing agency combed BUET's Sher-e-Bangla Hall where he was fatally beaten, and analysed footage from a closed-circuit camera installed there on Monday, said Dhaka Metropolitan Police's Additional Commision Krishna Pada Roy.
Abrar, a second-year student of electrical and electronic engineering, was found dead in the stairway in the early hours of Monday.
A resident of Sher-e-Bangla Hall, Abrar was called up from his room at 7:30pm on Sunday, said police, quoting the students of the hall.
Later, his body was found on the first-floor stairway of the hall at 2am.
There were numerous injury marks on his hands, feet and back, a doctor said, adding, "He died due to internal bleeding."
Classmates of Abrar claimed that BCL men beat him to death suspecting his involvement with Islami Chhatra Shibir.
Police officials visited the room 1011 of the dormitory where Abrar was allegedly beaten and other rooms and collected evidence, said Additional Commissioner Krishna.
“Whoever the criminal is will be brought to justice. We’ll find all of them,” he said.