Father of elementary school girl murdered by teacher: ”I listened to the scene on an app... It was 100% planned crime” (South Korea)

A first-grade girl was stabbed to death by a female teacher in her 40s at an elementary school in Daejeon, and the girl's father said the incident was a "planned crime."
On the afternoon of the 10th, Mr. B, the father of the murdered A-chan, returned to the hospital where A-chan was staying after the police finished their investigation of the family on the day of the incident and told reporters, "My child has been attending art school since last week.
He said, "The child attended the same school as the police and was the only child there until 4:40 p.m.," and added, "It seems likely that the perpetrator knew that the child would be alone and prepared the murder weapon himself. This is clearly a planned crime."
B also said that he had heard every sound from when he started looking for A-chan at around 4:50 pm until he found her. A-chan had a parental protection app installed on her mobile phone.
It is said that you can hear all the sounds around you in real time without making a phone call. Mr. B said, "I can no longer hear my children's voices, and when an old woman runs,
"I kept hearing sounds like heavy breathing, drawers opening and closing, and bags being unzipped," he said.
According to police and fire authorities, at around 5:50 pm on the 10th, a fire broke out in Gwangjo, Seo-gu, Daejeon.
A-chan, stabbed with a weapon, and a teacher from the school were found in the audiovisual room on the second floor of an elementary school in Kwangye-dong. A-chan was in the Dolbom classroom (a kind of after-school care) in the school after school.
When A-chan was found, she had serious injuries on her shoulders, face, hands, etc., and was in cardiac arrest. The teacher next to her had been stabbed in the neck and arms with the murder weapon, but was still conscious.
Although they administered cardiopulmonary resuscitation to the student and rushed him to the hospital, he later died. The teacher confessed to the crime to the police around 9:00 p.m. on the same day. The teacher was not a temporary contract worker or an outside instructor, but was employed by the school.
The teacher is said to be a regular teacher at the school. Police plan to investigate the exact motive and circumstances of the crime once the teacher recovers from treatment at the hospital. The school has informed students and parents that the school will be closed on the 11th.
I told him that.