The incident unfolded on Monday morning at around 8.33am at a high school in Cheongju, a city in North Chungcheong province located about 110km southeast of Seoul.
According to The Korea Herald, the 18-year-old attacker – a second-year student – was in a counselling session with a special-education teacher when he suddenly began strangling the educator.
He then chased the teacher into the hallway and allegedly began slashing at other staff members with what appeared to be a utility knife.
The school’s principal and two staff members were left with stab wounds to the chest, abdomen and back, and were transferred to hospitals for treatment.
Members of a South Korean Police Crime Scene Investigation team probe a high school in Cheongju on April 28 after a knife attack by a student left seven injured. Photo: AFP
The counsellor was also hospitalised due to shock and breathing difficulties.