Mizanur Rahman Mizan, a roommate of slain Buet student Abrar Fahad, provided Buet Chhatra League leaders with information on Abrar's alleged connection with Islami Chhatra Shibir.
"Mizan told the BCL leaders about the discussions he had with Abrar, which convinced the leaders that Abrar had links to Chhatra Shibir," said Sub-Inspector Mazharul Islam of Chawkbazar police.
The charge sheet submitted to the Chief Metropolitan Magistrate Court in Dhaka on Wednesday revealed that later, the Chhatra League men beat Abrar to death in a room of Sher- e-Bangla Hall on October 6.
Detective Branch of police pressed charges against 25 current and former members of Buet Chhatra League over the murder.
Among the accused, 21 have been arrested while four are absconding.