Cheorwon County (Cheorwon-gun [ˈtɕʰʌ̹ɾwʌ̹n‿ɡun]), also spelled Chorwon, is a county in Gangwon Province, South Korea. It is located right next to the border with North Korea. From Wikipedia
The South Korean military confirmed the incident, notifying North Korea immediately to prevent escalation, with no unusual activity reported from the North.