Fourteen people were killed and 11 others sustained injuries when a ventilation window at an outdoor theatre near Seoul, where a music concert was being held, collapsed Friday.The people were watching a K-Pop performance at an outdoor theatre in Seongnam, Gyeonggi province, when the incident happened, Xinhua reported citing Yonhap news agency. Dozens of people, who were standing above the ventilation window for a better view, fell from a height of 10 metres when the window collapsed at about 5.50 p.m.. according to police.About 700 people had come to the outdoor theatre in Seongnam, a satellite city of South Korea's capital Seoul, for the evening concert.