Farmers clash with riot policemen during a protest outside the Greek Agriculture Ministry on March 8, 2017 in Athens, Greece. Two people were detained after the windows of two police vans were smashed as approximately 1,000 farmers, mainly from the island of Crete, took part in the protest. (Photo by Nikolas Georgiou/ZUMA Wire/Rex Features/Shutterstock)

Stray dogs stand on tombs in Diamond Hill cemetery in Hong Kong, China, 04 April 2017. According to the lunar calendar, the Qingming Festival is observed on 04 April . The Qingming Festival, also known as Tomb-Sweeping Day, is marked by Chinese people by going to the cemetery to cleaning up tombs, bring flowers, and making offerings to their ancestors. (Photo by Jerome Favre/EPA)

Seiichiro Nishimoto, CEO of Shelter Co., poses wearing a gas mask at a model room for the company's nuclear shelters in the basement of his house in Osaka, Japan on April 26, 2017. With nearby North Korea increasing its show of power day by day with missile launches and nuclear tests, people in Japan are preparing for the worst by building private nuclear shelters, Reuters reports. (Photo by Kim Kyung-Hoon/Reuters)

Joe Deedon, president of TAC ONE Consulting, demonstrates searching for a shooter in a middle school during an Active Shooter Response course offered by TAC ONE in Denver April 2, 2016. According to TAC ONE, the course, which is offered for the first time to concealed weapons permit carrying civilians, is designed at preparing people to effectively save lives prior to the arrival of law enforcement at an active shooter incident. (Photo by Rick Wilking/Reuters)

Members of the Cyclophonica band play instruments as they make a stop during a ride in Rio de Janeiro May 17, 2015. The Cyclophonica band was formed by a group of musicians riding bicycles around the city, mixing sport and culture and entertaining people on the streets, according to its founder Leonardo Fuks. (Photo by Pilar Olivares/Reuters)

An actor plays an injured passer-by during Exercise Strong Tower, the scene of a mock terror attack at a disused underground station in central London, Britain June 30, 2015. London police held their biggest-ever terrorism drill on Tuesday, pitting the emergency services against a group of marauding attackers, nearly 10 years since four young British Islamists killed 52 people in suicide bombings on London's transport network in July 2005. (Photo by Peter Nicholls/Reuters)

Tourists standing near the sea shore are hit by a wave, which surged past a barrier under the influence of Typhoon Chan-hom, in Qingdao, Shandong province, China, July 12, 2015. One of the most powerful typhoons to strike eastern China in decades disrupted air, rail and sea transport on Saturday after forcing the evacuation of more than a million people from the provinces of Zhejiang and Jiangsu, state media reported. (Photo by Reuters/Stringer)

Revelers dance and shout as they listen to music, in front of the main stage, during the 21st Woodstock Festival in Kostrzyn-upon-Odra, Poland July 31, 2015. An estimated 200,000 people attended the ongoing festival, a brainchild of Polish journalist and social campaigner Jerzy Owsiak, on Friday. Owsiak initiated the event to say thank you to those who donated money to his GOCC charity organisation that delivers medical care for children. (Photo by Kacper Pempel/Reuters)