In this September 4, 1963, file photo, a police officer carries off a demonstrator holding a Confederate flag after a group of demonstrators protested enrollment of two African-Americans at Ramsay High School in Birmingham, Ala. The Confederate battle flag has been removed from South Carolina's Statehouse grounds, in the wake of the massacre of nine African-Americans, including a state senator, at an historic black church in Charleston in June 2015. (Photo by AP Photo)

In this October 6, 1976, file photo, a right-wing student, center foreground, draws his arm back to strike a captured and wounded leftist student being taken by police to an ambulance in during a student massacre in Bangkok, Thailand. This year’s anti-government protests are seeking new elections, a more democratic constitution and an end to intimidation of political activists. Their speeches have repeatedly highlighted the 1976 tragedy, piquing the interest of the current generation in what their forebears faced. (Photo by Neal Ulevich/AP Photo/File)

Performers re-enact the 1947 massacre of Taiwanese intellectuals by mainland China's Nationalists troops during the inauguration ceremony of Taiwan's President Tsai Ing-wen in Taipei, Taiwan, Friday, May 20, 2016. Taiwan inaugurated Tsai as its first female president on Friday, returning the pro-independence Democratic Progressive Party to power amid new concerns over increasingly fractious relations with Beijing and a flagging economy. (Photo by Chiang Ying-ying/AP Photo)

A woman waits to hear about her sister, a teacher, following a shooting at the Sandy Hook Elementary School in Newtown, Connecticut. A man killed his mother at their home and then opened fire inside the elementary school where she taught, massacring 26 people, including 20 children, as youngsters cowered in fear to the sound of gunshots reverberating through the building and screams echoing over the intercom. (Photo by Jessica Hill/Associated Press)

Hooded demonstrators vandalise a shop window in Mexico City, during the commemoration of the 50th anniversary of the 1968 Tlatelolco student massacre, on October 2, 2018. Fifty years ago, Mexican troops opened fire on student demonstrators, killing hundreds just days before Mexico City hosted the 1968 Olympics – one of the darkest episodes in a year of global turbulence. (Photo by Ronaldo Schemidt/AFP Photo)

Jewish children in fancy dress during the annual Jewish holiday of Purim on March 12, 2017 in London, England. Purim is celebrated by Jewish communities around the world with parades and costume parties. Purim commemorates the defeat of Haman, the advisor to the Persian king, and his plot to massacre the Jewish people, 2,500 years ago, as recorded in the biblical book of Esther. (Photo by Dan Kitwood/Getty Images)

Supporters of Ratko Mladic wave flags with his picture and reading in Serbian “Serbian hero” during a rally organized by the ultra nationalist Serbian Radical Party in front of the Parliament building on May 29, 2011 in Belgrade, Serbia. Some 7,000 supporters of the former Bosnian Serb army chief Ratko Mladic, who was arrested on Thursday in a village in Serbia after 16 years on the run, took to the streets of Belgrade, to hear speeches and protest Mladic's arrest. Mladic, who is facing extradition to the The Hague, is accused of war crimes, including the 1995 massacre of 7,500 Muslin men and boys in Srebrenica. (Photo by Srdjan Stevanovic/Getty Images)

Boys pan for gold on a riverside at Iga Barriere, 25 km (15 miles) from Bunia, in the resource-rich Ituri region of eastern Congo February 16, 2009. Ituri is one of many areas of the country to have experienced bitter ethnic conflict between rival tribes in recent years. Massacres have left tens of thousands dead. It is this fighting that led U.S. authorities to take the unprecedented step of naming Congo in section 1502 of the Dodd-Frank financial regulation act, which says U.S.-listed companies that source gold, tungsten, tantalum and tin from Congo or its neighbours must assure the U.S. stock exchange regulator that their business is not helping fund conflict. (Photo by Finbarr O'Reilly/Reuters)