South Koreans are searching for answers as the country mourns after more than 150 people were killed in a stampede during Halloween festivities in a popular party district.

Officials said 82 people were also injured in the incident Saturday night in Seoul’s Itaewon area, which had been packed with crowds ahead of the Monday holiday.

It is the deadliest mass-crushing incident in South Korea’s history. Officials say most of the victims were young people in their teens and twenties.