A teenager has killed his step-mother with a knife. The incident happened Saturday morning in Agyaragu area of Lafia, the capital of Nasarawa State. Eyewitnesses said, he cut her throat with a kitchen knife. Our reporter said children of the deceased have armed themselves and are in search of their half brother to avenge the death of their mother. We are yet to ascertain what transpired between the duo before the incident. Police have cordoned off the house already. A police officer, who preferred anonymity, said they were about to file a report to their headquarters who will address the press afterwards.