``He brought a deadly weapon into the store.'' Why did fellow employees report this? = South Korea

Police have applied for an arrest warrant against a part-time store employee who is a teenage high school student and threatened him, saying, ``Don't arrive to work any more. I'll kill you.''
On the 20th, the Seongnam Jungwon Police Station in Gyeonggi-do (Gyeonggi-do) reported that a part-time employee at the fast food restaurant where he works
It has been revealed that an arrest warrant has been applied for suspect A, who is in his 20s, on suspicion of threatening to kill a store employee (preliminary murder).
At around 12:50 noon on the 19th, Suspect A went to a certain Fast Food restaurant where he was working as a manager.
He is accused of threatening B, a part-time employee and a teenage high school student, in the chat room of the store's staff group, saying, ``Don't arrive to work any more. I'll kill you.''
It was learned that the two had a disagreement during a business-related conversation and got into an argument.
Suspect A bought the murder weapon nearby when Mr. B replied that he would come to the store after school.
I waited for Mr. B to come. Other employees who were at the store at the time saw Suspect A bringing a deadly weapon into the store and were unable to contain their anger, so they called the police.
Suspect A, who was caught red-handed, told the police that he was trying to scare Mr. B.
The police took into account the high possibility that Suspect A's actions would lead to the actual crime.
, applied for a warrant for arrest on suspicion of pre-murder.