Military vehicles surround a wreckage of a trolleybus, in Volgograd, Russia, Monday, December 30, 2013. A bomb blast tore through a trolleybus in the city of Volgograd on Monday morning, killing at least 10 people a day after a suicide bombing that killed at least 17 at the city's main railway station. Volgograd is about 650 kilometers (400 miles) northeast of Sochi, where the Olympics are to be held. (Photo by Denis Tyrin/AP Photo)

A huge supercell dominates the Texas skyline like an atomic bomb explosion on April 11, 2015 in Lubbock, Texas. A huge supercell dominates the Texas skyline like an atomic bomb explosion. These incredible images were taken on April 11th, by photographer Darin Kuntz who has spent in his entire life in so-called Tornado Alley. And Darin confirmed that he snapped the storm standing in his backyard in Lubbock, Texas. (Photo by Darin Kuntz/Barcroft Media)

Londoners sleep on the platform and on the train tracks at Aldwych Underground station,London, during heavy all night Nazi bombing raids, October 8, 1940. (Photo by AP Photo)

Somali security officers gather at the scene of a car bomb attack at the base for the African Union forces in Mogadishu, Somalia, 26 July 2016. Media reports say at least 10 people, including the security guards at the base which is located at Mogadishu's airport, have been killed after two car bombs exploded at the base. Somalia's Islamist militant group al-Shabab has claimed responsibility for the latest attack. (Photo by Said Yusuf Warsame/EPA)

A U.S. Army B-24 Liberator Bomber is hailed by a ground crewman as it takes off over a line of shark- nosed fighter planes at an advanced base in China on a mission on October 10, 1943, to bomb Japanese installations. (Photo by AP Photo)

Syrian civil defence volunteers, known as the White Helmets, rescue a boy from the rubble following a reported barrel bomb attack on the Bab al- Nairab neighbourhood of the northern Syrian city of Aleppo on November 24, 2016. (Photo by Ameer Alhalbi/AFP Photo)

A Lebanese man carries an injured woman away from the site of a car bomb explosion in a Shiite area and stronghold of the Lebanese militant group Hezbollah at the southern suburb of Beirut, Thursday January 2, 2014. A large explosion has rocked a stronghold of the Shiite Hezbollah group in the southern suburbs of the Lebanese capital. (Photo by Hussein Malla/AP Photo)

British troops covered in flames from a petrol bomb thrown during a violent protest by job seekers, who say they were promised employment in the security services, in the southern Iraq city of Basra, March 22, 2004. (Photo by Atef Hassan/Reuters)