South Korea man arrested for assaulting high school student over second-hand goods trade

A 20-year-old man was arrested by police for assaulting and threatening a high school student in front of Olympic Park in Seoul, South Korea on Children's Day.
The Songpa Police Station in Seoul arrested a man named A on suspicion of special assault.
On the 9th, the police announced that they had arrested 20 people on the spot and that they were currently investigating the matter. A is said to have been carrying a knuckle-wrapped knife near Olympic Park in Songpa-gu, Seoul, around noon on the 5th of this month, when he shot a high school student named B with a knife.
At the time of the crime, Mr. A was carrying a knife measuring approximately 28cm in length, but it is reported that he did not brandish it or cause any direct harm.
The police arrested Mr. A at the scene and, taking into consideration his history of mental illness, had him admitted to a nearby hospital.
In cases where the person is in a mental health facility, the doctor and police must agree to admit the person to the facility. As a result of the investigation, Mr. A was dissatisfied with an item he had previously purchased from Mr. B through a second-hand transaction and requested to meet him again.
During the investigation, Mr. A stated that he was angry because he was sold a broken BB gun. Mr. B reportedly had no major injuries other than scratches.