UN Secretary-General Antonio Guterres was deeply shocked and saddened by the heinous mass shooting in an elementary school in Texas, the United States, said his spokesman. It is particularly heart-wrenching that most of the victims are children, said Stephane Dujarric, the spokesman, in a statement on Tuesday. The Secretary-General extends his heartfelt condolences to the families and loved ones of the victims and to the entire community, the statement added. An 18-year-old man opened fire at an elementary school in Uvalde, Texas, on Tuesday afternoon, killing 21 people, including 19 children, Xinhua news agency reported.