In this picture taken on September 24, 2016, relatives grieve their lost one, an alleged drug user/dealer gunned down by unidentified gunmen in Manila. Philippine President Rodrigo Duterte defended his threat to kill criminals as “perfect” and vowed no let-up in his war on crime, as the death toll surged past 3,700. (Photo by Noel Celis/AFP Photo)

Dan Copeland, left, and Alex Morneau of Biddeford, Maine, former high school cheerleaders, perform back flips while enjoying the record breaking heat, Thursday, May 18, 2017, at Old Orchard Beach, Maine. The temperature climbed well into the 90s in many locations throughout the state. (Photo by Robert F. Bukaty/AP Photo)

Student protestors, including one girl with a camera, struggle with soldiers from the Chinese Army, the PLA. Tiananmen Square, 1989. (Photo by Jeff Widener/Associated Press)

“The Independence day”. While on storm chasing expeditions in the Tornado Alley in USA I have encountered many photogenic supercell storms. This photograph was taken while we were approaching the storm near Julesburg, Colorado on My 28th, 2013. The storm was tornado warned for more than one hour, but stayed an LP storm through all its cycles and never produced a tornado, just occasional brief funnels, large hail and some rain. Photo location: Julesburg, Colorado, USA. (Photo and caption by Marko Korošec/National Geographic Photo Contest)

A Kenya Wildlife Services (KWS) veterinarian and security personnel back away from a tranquilised black-Rhino calf August 30, 2017 after she appeared to prematurely overcome the sedative at the Nairobi National Park, during an identification-tagging excercise to ease quick identification of resident rhino during anti-poaching patrols. (Photo by Tony Karumba/AFP Photo)

Thailand’s Sanctuary of Truth is an all-wood building filled with sculptures based on traditional Buddhist and Hindu motifs. It is covered in intricate wood carvings, meant to depict complex ideas about ancient thought, human responsibility, and the cycle of life. (Photo by Yury Taranik/Getty Inages)

In this November 11, 2017 photo, children dressed in traditional outfits play during the Azorean Culture Festival which celebrates the culture of the Azores, the Portuguese island chain in the mid-Atlantic, in Enseada de Brito, in Brazil's Santa Catarina southern state. “We have to make sure that our culture always stays alive, not let it die”, said Andre Cordeiro, who leads one of the singing and dancing groups that performed this year. “We are able to pass it on from generation to generation”. (Photo by Eraldo Peres/AP Photo)

School teachers and staff members take part during an active shooter training at James I. O'Neill High School in Highland Falls, New York, U.S., December 12, 2017. (Photo by Eduardo Munoz/Reuters)