Shoes representing the children killed in school shootings since Sandy Hook Elementary School shooting in 2012 are seen on the lawn in front of the Capitol in Washington D.C., the United States, on March 13, 2018. An activist group on Tuesday placed 7,000 pairs of shoes on the lawn in front of U.S. Congress, in protest against lawmakers' inaction in face of frequent school shootings in the country. (Xinhua/Ting Shen)