We have to warn you some of the images we're gonna share are graphic.

Authorities are still investigating exactly what caused this crowd crush,

but emergency officials first began receiving reports of people buried in crowds on Saturday evening.

There were thousands of people out that night in an area of the city with very narrow streets, as you can see; they're packed in alleys.

And witnesses say people were trapped and panicked because they couldn't breathe, with dozens of people being administered CPR on the sidewalks.

And I, like, turned around and I told the crowd, "You can't come this way; people are dying."

Now, police say they have confirmed the identities of nearly all of those killed, as families attempt to reunite with loved ones lost in the chaos.

President Biden and the First Lady, by the way, have both offered their deepest console⏤condolences to the families of those impacted by this horrific tragedy.

Let's take you to Seoul, now, and CNN's Will Ripley, who is on the scene shortly after this happened.

Will, have officials gotten any closer to understanding exactly how all of this unfolded?

It seems as if this may have simply been a case of so many people so excited to be out for the first Halloween after COVID restrictions.

So, three years of restrictions, and people were packing into this area.

We're actually now behind the alleyway that we showed you just now on video.

And you can see this is where a lot of people were receiving CPR; you saw lines of bodies down the streets.

And what's really, really striking to me is, you see that bag there with a shoe and, you know, you see people's Halloween costumes.

I remember seeing one of the bodies that was rolled by our live position yesterday,

and there was a sheet covering the stretcher, but you could see she had a beautiful, glittery princess dress on for Halloween.

And anybody who knew her would have known that that was her just by seeing the costume,

and you think about her⏤this young... this one woman's parents, her family, her friends, and it's just really heartbreaking.

97 of those who were killed are women, 56 men out of the 153 deaths.

And they come from⏤not just here in South Korea, the majority from South Korea, but, really, all over the world.

I mean, the list up⏤just updated here, Norway, Australia, Japan, Sri Lanka, Thailand, Iran.

All of these people⏤many of them in their twenties, in their thirties⏤out here having a great time and they never came home.

Halloween, horror, and heartbreak in Seoul's popular nightlife district.

Nightmare scenes⏤the narrow alleys of Itaewon lined with lifeless bodies, many in costume.

Frantic first-responders trying to save them.

This is a row of stretchers that we initially thought were waiting for potential survivors of this incident at a Halloween party where thousands of people were packed into a relatively tight area.

But in fact, we've now realized that these stretchers are being used to bring back bodies.

And we have just seen body after body rolling pass here.

[Korean] In the 76 injured...

"Most of those hurt or killed in their late teens and twenties," the local fire chief says, "young people from South Korea and beyond."

Witnesses say Itaewon's iconic Halloween festivities always draw an international crowd.

This video on Twitter shows an apparent lack of crowd control.

A sea of bodies pouring into a tiny area; an ominous warning telling people to be careful.

Police and emergency crews rushed to the scene shortly after 10 p.m. local, Saturday night.

Yonhap News Agency reported emergency lines flooded with calls from people in the packed area, saying they were stuck, suffocating.

Some who fell down apparently crushed under a growing pile of people.

Official causes of death not confirmed, but Yonhap reporting dozens suffered cardiac arrest.

And I saw the people's like going to the left side, and I actually saw the person actually get into the the opposite side.

So, actually, the person in the middle, they got jammed, and they... they have like, you know, no way to communicate, and they, like, you know, they cannot breathe.

The fire chief calls this a "presumed stampede".

The investigation is ongoing.

Social media video shows emergency crews struggling, pulling injured and unconscious victims from the narrow alleyways still jammed with hundreds, if not thousands, of people.

South Korea's president Yoon Suk-yeol holding an emergency cabinet meeting; the tragic incident now being treated as a national disaster.

Authorities say hospital beds and morgues (are) filling up fast.

President Yoon making rapid identification of victims a top priority.

Anxious families and friends desperately waiting for word, waiting for loved ones who left for a night of Halloween fun and haven't come home.

As of about an hour ago, there were 4,100 missing persons cases filed.

There were about 100,000 people out here last night⏤tonight was actually supposed to be an even bigger night.

This is one of the alley⏤the alley, actually, right next door, just down the block from where this happened.

This was supposed to be packed tonight.

And you can see that it's completely shut down.

This space, maybe six and a half feet across.

Guys, can you imagine being stuck in the middle here, with literally thousands of people in this small area packing and pushing you?

It... it's hard to wrap your mind around how terrifying that must have been for those people who were essentially crushed to death or for those who slipped and fell and had people piling up on top of them.

Some people so desperate, you know, they were trying to climb up these walls here, just jumping in and grabbing for anything they could to get up above the crowd of people.

There's a lot of questions that need to be answered here in South Korea.

Why were so many people allowed to pack into a narrow space like this?

Where was the crowd control?

The... those... some of the images that we've been showing you, they were from an hour, two hours before this deadly incident.

Was there nobody sounding the alarm saying, "Hey, too many people; let's clear them out before something horrible happens."

I mean, these are the really tough questions that they're having to ask here.

But tonight, as you see, it's all about, well, most people who were here last night want nothing to do with this place now.

It's empty.

Aside from a handful of reporters and the police blocking off the area, and, of course, those shoes and the pieces of people's Halloween costumes just sitting in trash bags.

(I) Guarantee you, a lot of the pieces of costumes there come from people who... who didn't make it out alive yesterday.

Just heartbreaking details to think about, you know, these costumes and how recognizable some of the victims may have been, Will.

And ju... just to give it some context, I mean, that's an eerie silence that we're seeing and not hearing, right?

Because Itaewon, as some of you may know, I've been there before.

You know, it's a popular entertainment night district, a place that, you know, a lot of foreigners like to frequent.

It's very popular with US soldiers, a big expat community.

And just... just a quick question.

Were the crowds unex⏤I mean, I guess, such large crowds unexpected?

Was there a parade, or what was exactly supposed to take place last night there?

Well, there were a lot of different parties thrown⏤and I should point out, Emma,

I mean, I've been to Seoul dozens of times for work covering North Korea, or just, you know, covering South Korea over the years; it's been a few years since I've been here.

And I can't count how many nights I have been along this exact same street with friends.

I celebrated my birthday at that restaurant right there.

This is the place that you go if you want to have some drinks, have... have a meal.

So, this feels... it feels very personal for anybody that has... that has come to Seoul and come to Itaewon, which is a very, very popular, iconic place, especially on Halloween.

Halloween is always one of their biggest nights.

I think people knew that this night was gonna be huge.

I mean, there were live streams; people were saying this is gonna be the most wild Halloween party in Asia, you know,

because people were so excited to just come back out and not have to wear a mask on Halloween.

Over three years, they had to wear a mask on Halloween, and they⏤and there were limits on crowd size.

That was not the case this year, and so it...

Well, you know, in terms of why people died, was... was the fact that alcohol was consumed a factor in all of these cardiac arrest cases?

Some doctors are saying that mi⏤that might be the case.

It's still, you know, too early to, you know, to... to figure that out,

because with such a high volume of bodies that still, some of them unidentified, you know, still, you know, families waiting to be notified,

it... it's just going to take time.