South Korean police are investigating what caused a crowd surge that killed more than 150 people during Halloween festivities in Seoul last weekend in the country's worst disasters in years, as President Yoon Suk Yeol and other residents paid respects to the dead at temporary mourning sites. Saturday's deadly crowd surge was concentrated in a sloped, narrow alley in Seoul's Itaewon neighbourhood, a popular nightlife district, with witnesses and survivors recalling a “hell-like” chaos of people falling on each other “like dominoes." They say the entire Itaewon area was extremely jammed with slow-moving vehicles and party goers clad in Halloween…