A mourner places flowers, Tuesday, at the fence of the school in Daejeon, where a 7-year-old student was killed by a teacher the previous day. Newsis

A teacher in Daejeon said she stabbed a 7-year-old girl to death at school because she was angry for not being allowed to teach students after returning to work, according to the police on Tuesday.

The Daejeon Seobu Police Station said the suspect was being investigated after confessing to killing the student at an elementary school on Monday. The two did not know each other beforehand, police added.

Police found the victim, Kim Ha-neul, unconscious with many stab wounds inside the audiovisual room on the second floor of the school building, along with the teacher who was also bleeding.

The girl was immediately transported to a nearby hospital where she was pronounced dead as a result of blood loss.

The teacher, who was conscious at that time, was taken to an operating room where she was treated for what appeared to be self-sustained injuries.

The suspect told police that she lured Kim into the room by offering her a book, then strangled and stabbed the girl, police said.

The teacher said she was angry for being prohibited from teaching. She said she was angry at the vice principal who made that decision. Police said they are looking into that claim.

The suspect said she was looking for a student to target randomly, according to police. She had simply planned to attack the last student coming out of the classroom, and Kim was unfortunate to be the last child to leave that day. The suspect also claimed she planned to kill herself afterward.

Police said they found that the suspect had bought a knife at a store near the school during the lunch break, hours before the attack.

Investigators said they will detain her for further questioning on suspicion of premeditated murder.

A portrait of Kim Ha-neul is set up at a funeral hall in Daejeon, Tuesday. Yonhap

Kim was waiting for a shuttle bus to arrive after the school's after-school program ended. When she did not show up at 4:40 p.m. for her private art class, the academy called her family about 10 minutes later, which alarmed them and prompted a police search.

Kim's father said he sensed that she could be in danger as he heard unusual sounds in real time through an app installed in her mobile phone.

"From 4:50 p.m., I didn't hear Ha-neul's voice. I could only hear a gasping sound from an old lady as if she was panting after running, as well as sounds of someone opening and closing a drawer and unzipping something like a bag," he told reporters.

About an hour later, Kim's grandmother found the teacher at the audiovisual room covered with blood, so she alerted police officers to search her and the room, where they also found the girl.

According to the police and the regional education authority, the teacher took a leave of absence from Dec. 9, 2024, over symptoms of depression. She was expected to take six months off, but came back after about 20 days, expressing her intention to return to work early and submitting a medical certificate claiming she was ready to return to the classroom, according to an official at the Daejeon Metropolitan City Office of Education.

Only four days before the killing, the suspect showed violent behavior toward a colleague after simply being asked how she was doing.

According to Kim's father, dozens of stab wounds were found all over the child's body, including on her hands — indicating that she resisted.

"Police told me not to look at my daughter's body at the storage (inside the audiovisual room) because it would be difficult … My daughter became a star in the sky. There should never be another case like Ha-neul's," the father said. "I hope the government will come up with measures to prevent such incidents from happening again by pushing to revise the law or strengthen rules on teachers with a history of mental health problems."

Police said they asked the National Forensic Service to conduct an autopsy on Kim's body to find the exact cause of her death.