A 15-year-old from Khayelitsha is under police guard in hospital after he sustained injuries during an altercation in which he allegedly stabbed and killed a 17-year-old in Cape Town’s city centre on Friday.Western Cape police spokesperson Lieutenant Colonel Andrè Traut said the incident had taken place on the Grand Parade."The circumstances surrounding the murder and attempted murder are being investigated following an incident late this afternoon on the Grand Parade, where a 17-year-old male was allegedly stabbed to death during a fight with a 15-year-old male."The 15-year-old will be detained as a suspect on a murder charge once he has been discharged from hospital," said Traut.Both are from Khayelitsha and attend school in Woodstock.Also read: Violence in SA's schools is worse than you think, and spanking is part of the problem"During our investigation on the scene, several youths were questioned and searched. This resulted in the arrest of four suspects, three for the possession of dangerous weapons and one for the possession of dagga," he added.The City of Cape Town's Wayne Dyason said that at about 15:55, a member of the public came to the law enforcement mobile office on the Grand Parade to report that a group of pupils were fighting in Strand Street next to the Castle."Officers then went to investigate and found two injured pupils, one was hit with a brick in the face and another had a stab wound to the heart. Officers then called the police because the pupil with the stab wound appeared to be not breathing."Medics arrived and declared the stab victim dead, while the suspect was taken to Somerset Hospital. The police arrived on the scene and searched some pupils at the crime scene. One pupil was found to be in possession of a big flip knife and [has been] arrested," he said.