According to Yonhap News, both students live in the same apartment complex and A threatened B with a knife in the apartment elevator. A held a 20cm (~8 inch) knife against B until they reached the first floor. The entire incident was caught by the elevator's camera.
Fortunately, B was able to leave the elevator without harm. The police were notified of A's actions after B informed his parents of the threat.
During the investigation, A revealed, "I took out the weapon after I told him I had something fun to show him. But I had no intentions to harm."
The parents of B claim that B is traumatized and showing signs of social anxiety disorder.
The neighbors of the apartment are also in fear as a kidnap and murder case of an elementary student occurred in the same town back in March.