Less than two hours later, people began spontaneously falling over and then trampling on each other in a tight knot of bodies that made it all but impossible to move or breathe.
To avoid too many bodies being crushed in too narrow of a space, such street events need "months of planning" by experts, Kant in the Netherlands said.
This includes calculating visitor capacity beforehand and then counting and monitoring the size of the crowd and possible bottlenecks either on the ground or via CCTV.
"During the event, if maximum capacity is reached, further access to that area should effectively be shut off," Kant added.
It was only around 2:00 am, or more than seven hours after the first emergency call, that officials banned anyone except officials and medical workers from entering Itaewon.
National police chief Yoon Hee-keun acknowledged that officers had failed to properly responded to the many citizen calls warning of danger, while the interior minister promised an investigation into what exactly happened in Seoul.
"I am 100 percent convinced this tragedy was preventable," said Kant.
"Crowd crushes or crowd disasters were and are always predictable, thus preventable."
