Tens of thousands of people descended on the location in central Seoul on Saturday night to celebrate Halloween, but as the numbers grew, panic broke out, with some witnesses reporting that it became difficult to breathe and impossible to move.

More than 150 people, largely young adults, were killed as a large Halloween party throng pushed into a small lane in a popular nightlife area of Seoul. South Koreans mourned and looked for relatives who may have been lost in the "hell-like" mayhem. As families throughout the nation grieve and look for missing loved ones, authorities have now opened an urgent investigation to determine how what was supposed to be a night of celebration went so brutally wrong.  

As of this writing, it is still unclear what prompted the mob to pour into the downward alley in the Itaewon neighborhood on Saturday night. People "fell on top of one other like dominoes," according to witnesses, and several victims were gushing from their lips and nostrils as CPR was being administered. 

What happened in Itaewon 

Before the mob turned deadly, witnesses told CNN that there was little to no crowd control. Videos and images shared on social media show a crowded street with people standing shoulder to shoulder.

For that location and for residents of Seoul, who are used to crowded streets and subways in a city of roughly 10 million, crowds are not unusual.

According to one eyewitness, it took some time for people to recognize something was wrong because the music blasting from the nearby clubs and pubs competed with people's frantic screams. 

Many individuals didn't seem to understand the catastrophe was happening right in front of them. While some people around continued to sing and dance while wearing Halloween costumes, others were lying dead on the ground. 

An architect from Costa Rica named Ken Fallas visited Itaewon with some expat friends, and while there, he used his smartphone to record video of unconscious people being dragged out of the alley as other people yelled for aid. He claimed that the chaos was made worse by the loud music.

"When we just started to move forward, there was no way to go back," Fallas said, according to AP News. "We didn't hear anything because the music was really loud. Now, I think that was one of the main things that made this so complicated." 

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Pope prayed for victims, Bishops gives advice

Pope Francis spoke on the tragedy in the capital of South Korea on Sunday during the Angelus prayer. 

""Let us pray to the Risen Lord for all those-mostly young people-who died last night in Seoul from the tragic consequences of a sudden crowd stampede," the Pope said, according to Vatican News.

On the other hand, the Catholic Bishops Conference of Korea said that South Koreans must "break the cycle of injustice and irresponsibility that has become a common practice in this society."

"To do that, we must first be faithful to our respective roles," the Bishops added in the same report published in Vatican News. "Authorities must thoroughly examine the cause and process of this tragedy, and ensure that irresponsibility and oblivion are not repeated."

South Korea weeklong national mourning

Early on Sunday, just hours after a crowd surge during Halloween celebrations in a popular Seoul nightlife district resulted in at least 153 fatalities-mostly young adults in their teens and 20s-and more than 100 injuries, President Yoon Suk-Yeol of South Korea declared a weeklong period of national mourning. 

At least 20 foreign nationals, including those from the United States, Norway, Australia, China, Russia, Uzbekistan, Vietnam, Kazakhstan, Sri Lanka, and Iran, perished in the Itaewon nightclub district of Seoul on Saturday night, according to the South Korean Ministry of Interior and Safety; several of the victims are still unidentified. 

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