Mother of Bulbul Ahmed, a SUST student who was stabbed to death on Monday last, has urged the Prime Minister to take step to ensure punishment of the killers of her son. Bulbul’s mother Yasmin Begum made the request when she went to the provost’s office of Shah Poran Hall of Shahjalal University of Science and Technology (SUST) on Sunday to receive his son’s belongings. The victim’s siblings were also present at that moment. Also read: SUST student murder: Knife used in killing, victim’s mobile phone recovered Terming the murder as pre-planned, victim’s sister Sohagi Akter urged the authorities concerned to find out the actual culprits through proper investigation to ensure justice for her brother. “Real culprits might have hired killers in exchange of money. They might have killed him out of anger. Proper investigation will reveal everything,” she said. Sohagi said the identities of the main culprits will be disclosed if the detainees are placed on remand.   Bulbul, a third year student of the Public Administration Department of the university, along with his friends, went to the New Zealand area, adjacent to Shaheed Minar, on the campus on Monday last. At one stage, his friends rescued him as he was allegedly stabbed by muggers. Bulbul was first rushed to the university medical centre and later shifted to Sylhet MAG Osmani Medical College and Hospital where a doctor declared him dead around 7.45pm. Also read: Probe body formed over SUST student Bulbul's murder Besides, the authorities concerned of SUST formed a five-member probe body to look into the death. Police detained three people in connection with the murder of the SUST student on the campus on Monday evening. On Monday night, a case was filed at Jalalabad police station over the murder. Police on Wednesday recovered the knife used in the murder of Bulbul and his mobile phone set at Tilagaon near the university campus in Sylhet.