A teacher in his 60s at a high school in the Gyeonggi provincial city of Yongin who was found dead on a hiking trail on Sunday was reportedly subject to an audit over a student's accidental injury.

According to his family and authorities on Monday, the student was hurt severely enough to require surgery in June after being hit with a ball kicked by a classmate during the teacher's physical education class, although he was not present at the time of the accident.

Aside from authorities' inspection, the student's parents filed a complaint with the police against the teacher, surnamed Kim, for occupational negligence causing injury.

While the parents did not directly contact the teacher, he had talked about feeling great psychological pressure, according to his family.

He was found dead and in possession of a note by the police near an entry to a hiking trail at Mount Cheonggye in the Gyeonggi city of Seongnam Sunday morning, after his family reported that he was missing since the previous day. The police have since launched a formal investigation into the case.

Since the death of a young elementary school teacher in Seoul's Seocho District in July, three additional teachers, including Kim, have apparently ended their own lives over the past four days, with related investigations under way.