Seoul Halloween stampede: Five things to know about the horrific tragedy

More than 150 people, mostly young costumed partygoers in their teens and 20s, were killed in a crowd surge and stampede at a Halloween event in Seoul's popular Itaewon nightlife district.

It is the worst-ever stampede in South Korea's history, and President Yoon Suk-yeol has ordered a full investigation and vowed such a tragedy will never be allowed to happen again.

Here's what we know:

What happened?

Up to 100,000 people descended on Seoul's popular Itaewon district Saturday night for the first Halloween event without Covid-19 restrictions in three years.

Local merchants who have worked in the area for 30 years told AFP that the crowd had been "unprecedentedly large" this year but an earlier statement from the police indicated they only planned to deploy 200 officers.

Videos posted on social media showed the packed but initially peaceful crowd starting to panic as people kept pushing into a narrow, downhill alleyway, which was already wall-to-wall with revellers.

"People couldn't move forward and were pushing and pushing, and it was a steep hill so people were falling on top of each other, collapsing on top of each other," said eyewitness Jarmil Taylor, 40.

"People that were at the back were pushing and pushing because they had no idea what was going on in the front."

How did people die?

The majority of the victims were young women in their 20s, officials said, who died due to being trapped in the tightly-packed crowd in the narrow, sloping alleyway at the heart of the disaster.

In most stampede situations, experts say, people die of suffocation, and authorities in Seoul initially said that many victims were suffering cardiac arrest, which is the ultimate cause of death in such circumstances.

Eye-witnesses also described seeing people falling and getting trapped by the crowd before being trampled and crushed.

A delay in emergency first aid could also have led to more deaths, critics said, pointing to a lack of police at the scene which meant first responders initially struggled to reach victims through overcrowded alleyways.

This delay was critical as many victims who suffered cardiac arrests may have passed the crucial "four-minute" window before help arrived, experts said.

Where were the police?

On the other side of town, the interior minister said: a huge protest in Seoul's Gwanghwamun district Saturday also required a significant police presence, so many officers were deployed there.

In documents posted two days before the event, the police said they only planned to have 200 officers present for the Itaewon Halloween event.

Critics said this displayed a woeful lack of planning.

"This is a man-made disaster prompted by a lack of awareness about safety," said Shin Dong-min, a professor at the Korea National University of Transportation.

"Itaewon vendors and government officials should have had more preparations about a massive crowd gathering," he told YTN news.

And the rescue?

As a short-handed relief team struggled to assist scores of victims in cardiac arrest, passers-by jumped into help with first aid efforts and to perform CPR.

A video that circulated on Twitter showed dozens of people coming to perform CPR on victims sprawled in the street; other footage showed people in costumes carrying limp bodies on their backs.

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