Updated at 6.05pm: A 49-year-old man was arrested for allegedly killing his mother in a North Point building, police were quoted as saying by local radio on Wednesday. The case came to light when security guards found an injured man on a staircase of the building in Fort Street about 10am. When escorting the man to his flat, they discovered a 69-year-old woman with stab wounds lying on the floor of the flat. The woman, who was the man?s mother, was certified dead at the scene by ambulancemen, local radio reported. Following initial investigations, police officers arrested the 49-year-old man. Police have classified the case as murder, local radio reported. Further details on the case were not available on Wednesday afternoon.