South Korea's President Yoon Suk-yeol declared a period of national mourning on Sunday after a Halloween crush killed some 151 people in a packed nightlife area in Seoul. Yoon expressed condolences to the victims, mostly teenagers and people in their 20s, and his wishes for a speedy recovery to the many injured. "This is truly tragic," he said in a statement. "A tragedy and disaster that should not have happened took place in the heart of Seoul last night." A huge crowd celebrating in the popular Itaewon district surged into an alley on Saturday night, emergency officials said, adding the...