A 19-year-old Nelson Mandela University student is in police custody after he allegedly stabbed a fellow student to death.According to police spokesperson Captain Johan Rheeder, the incident took place at an off-campus residence on Saturday night.Rheeder said the two students, both aged 19, were drinking alcohol in one of their rooms when they started fighting."During the fight, the two students sustained stab wounds and were rushed to hospital. One later died while the other was arrested for murder," he added.In another incident, two NMU students drowned in a local pool, he said.The incident also took place over the weekend, and the police have opened an inquest docket.In a statement released by the university, it said it was mourning the deaths of the three students."The Nelson Mandela University community is mourning the passing of students in separate incidents over the weekend. Specific details relating to the incidents are under investigation by the South African Police Service, however, the university can confirm that three male students passed away."The university extends its heartfelt condolences to the families and friends of those who have lost their lives. Psychosocial support has been provided to students affected by these incidents and these support mechanisms remain in place," said the university. The South African Students Congress also expressed shock, saying it was saddened by the separate incidents."Amid the recent and sudden deaths of three of our students over the past weekend, the organisation took it upon itself to deploy comrades of the SRC to the affected residence yesterday in response to these unfortunate incidents."The organisation is deeply saddened to learn that three of our student's lives were cut abruptly short as life had so much in store for them as they were young and studying toward larger life ambitions. With this occurrence, the organisation would like to send its deepest condolences to the families affected by these unfortunate deaths."We are in communication with the university ... to have a memorial service for the families affected by this unfortunate experience. When all is finalised the details will be communicated," it said.