In one moment, thousands of Halloween revelers crammed into the narrow, vibrant streets of Seoul’s most cosmopolitan neighborhood, eager to show off their capes, wizard hats and bat wings.

In the next, a surge of panic spread as an unmanageable mass of people jammed into a narrow alley in Itaewon. Toppled revelers were trapped for as long as 40 minutes, stacked on one another “like dominoes” in a chaotic crush so intense that clothes were ripped off.

A stunned Seoul was just beginning on Monday to put together the huge scope of the crowd surge on Saturday night that killed at least 154, mostly people in their 20s and 30s, including foreign nationals. Officials said they expected more deaths because there were nearly 150 others injured, 33 of them in serious conditions.

Witnesses described a nightmarish scene as people performed CPR on the dying and carried limp bodies to ambulances, while dance music pulsed from garish clubs lit in bright neon. Others tried desperately to pull out those trapped at the bottom of the crush of people, but often failed because there were too many of the fallen on top of them.

“We were just stuck together so tightly we couldn’t even shift to call out and report the situation,” said one survivor, surnamed Lee. “We were strangers, but we held each others’ hands and repeatedly shouted out, ‘Let’s survive!’”