South Vietnamese forces escort suspected Viet Cong officer Nguyen Van Lem (also known as Bay Lop) on a Saigon street February 1, 1968, early in the Tet Offensive. Moments later, Lem was executed by Gen. Nguyen Ngoc Loan, chief of the national police. (Photo by Eddie Adams/AP Photo)

A cat walks in front of the body of a man killed by unknown gunmen in Manila, Philippines early October 18, 2016. A sign on a cardboard found near the body reads, “Pusher Ako, Wag Tularan”, which translates to “I am a (drug) pusher, don't be like me”. (Photo by Damir Sagolj/Reuters)

In this March 7, 1991 file photo, a U.S. Marine patrol walks across the charred oil landscape near a burning well during perimeter security patrol near Kuwait City. Twenty five years after the first U.S. Marines swept across the border into Kuwait in the 1991 Gulf War, American forces find themselves battling the extremist Islamic State group, born out of al-Qaida, in the splintered territories of Iraq and Syria. The Arab allies that joined the 1991 coalition are fighting their own conflicts both at home and abroad, as Iran vies for greater regional power following a nuclear deal with world powers. (Photo by John Gaps III/AP Photo)

A boy holds the remains of a mortar shell which hit a residential building in the village of Staromikhailovka, outside the separatist-held city of Donetsk, Ukraine, May 24, 2016. (Photo by Alexander Ermochenko/Reuters)

A cosplayer prepares before the start of the parade during the Metropoli (Media Culture and Entertainment Festival) in Gijon, northern Spain, July 3, 2016. (Photo by Eloy Alonso/Reuters)

Competitors pose backstage during the Arnold Classic South America bodybuilding event in Sao Paulo, Brazil, April 22, 2017. (Photo by Nacho Doce/Reuters)

A police officer walks along a street of the burning village of Smolenka near Chita on Monday, April 13, 2015. Russian authorities say out-of-control agricultural fires have killed at least 15 people, injured hundreds more and destroyed or damaged more than 1,000 homes in Siberia. The fires were started by farmers burning the grass in their fields, but spread quickly because of strong winds. (Photo by Evgeny Yepanchintsev/AP Photo)