A high school boy who tried to kill a female junior high school student on her way to school teased the crime two months ago (South Korea)

A high school boy who attempted to kill a junior high school girl by hitting her with a blunt object on her way to school on the first day of school had teased that he would harm the girl two months prior, but was unable to prevent the crime.
On the 19th, the Sangnok Police Station in Ansan, Gyeonggi arrested a high school student, Mr. A, on suspicion of attempted murder and is currently investigating the matter. Mr. A was arrested at 8:1 a.m. on the same day.
He is accused of hitting Mr. B on the head with a blunt object while he was on his way to school near a junior high school in Tonosaki-gu, Ansan City, on the 6th, and then brandishing the weapon, causing injury.
According to CCTV footage from the time of the crime, A followed B and suddenly attacked him from behind.
He hit Ms. B on the head with a blunt object. Despite Ms. B's resistance, he continued to assault her by grabbing her hair, and when Ms. B ran away while he picked up the dropped blunt object, he glared at her for a while and took the weapon out of his pocket.
A chased B for about 50 meters, brandishing the weapon, and was then subdued by the owner of a nearby store who witnessed the incident. He was then arrested red-handed by police officers who were called to the scene.
B was taken to the hospital with heavy bleeding, but his life is not in danger. A's bag, which was found to have a different type of murder weapon and a suicide note, contained the following:
The contents included details of previous plans to commit crimes but failures. A, who has an intellectual disability, is two years ahead of B at the same junior high school, and has known B as a senior and junior at school.
It was reported that they knew each other. The police believe that A-kun had been stalking B-san, which led to the crime. Prior to this, on March 31st of this year, B-san's father had contacted the police and said, "My daughter has known B-san for a year.
A report was received from a woman who was a victim of stalking, stating that a male student who was a student at her home was following her around despite her daughter refusing to comply. However, at the time of the report, Ms. B's father only provided the name of Mr. A and no contact information.
The police explained that they had not investigated or prosecuted A because A said that they did not know the details. The police had completed the procedures by informing B about the procedures for filing a complaint.
On June 27th of this year, A's school counseling teacher had consulted with A and then reported the matter to the school police. The counseling teacher said, "I spoke with A, but he said, 'I'm going to harm B and then commit suicide.'"
The school police officer informed B of this fact and took safety measures such as providing him with a smart watch, but B had not applied for the smart watch.
The school police officer, after consulting with A's parents, had A admitted to a psychiatric hospital. A was admitted to the hospital on the 2nd of last month, but was released about 20 days later on the 26th.
The police reportedly tried to persuade Mr. A's side to delay his discharge from the hospital, but Mr. A was determined to be discharged, so he was discharged.
The police conducted monitoring including calling A's side on the 13th of this month, but the incident
A made a statement to the police that he was angry because B didn't want to meet him. The police plan to apply for an arrest warrant as soon as they finish their investigation of A.
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