Police officers escort people from inside the shopping center as they respond to a shooting at the Olympia Einkaufzentrum (OEZ) at July 22, 2016 in Munich, Germany. According to reports, several people have been killed and an unknown number injured in a shooting at a shopping centre in the north-western Moosach district in Munich. Police are hunting the attacker or attackers who are thought to be still at large. (Photo by Joerg Koch/Getty Images)

In this August 1, 2014 photo provided by the National Park Service are male caribou antlers in the Oolah Valley, likely the result of a grizzly kill as he migrated south for the winter at the Arctic National Park and Preserve in Alaska. The nation's northernmost national park says its new management plan will have to consider the effects of a new industrial road to the mining district of Ambler, the first road that would be constructed within its Maryland-sized boundaries. (Photo by Cadence Cook/AP Photo/National Park Service)

A man takes a selfie in front of a fire from oil that has been set ablaze in the Qayyarah area, some 60 kilometres (35 miles) south of Mosul, on October 19, 2016, during an operation by Iraqi forces against Islamic State (IS) group jihadists to retake the main hub city. In the biggest Iraqi military operation in years, forces have retaken dozens of villages, mostly south and east of Mosul, and are planning multiple assaults for October 20. (Photo by Yasin Akgul/AFP Photo)

Pictures of deceased people are seen inside a chapel at a cemetery in the village of Smoljinac, Serbia, October 25, 2016. From a distance, the cemetery in the eastern Serbian village of Smoljinac looks like a residential neighbourhood eerily placed among graves. But once inside the grounds, after passing a section with the usual stone slabs, visitors find rows of small bungalows painted in pastel colours. They have one or two rooms, large windows and ornate plaques – some inside, some outside – memorialising the deceased. These are the burial chapels of Smoljinac, cosy cabins with a furnished room inside, a storage place for wreaths and funeral paraphernalia, and the family crypt below. Some even have electric power inside. (Photo by Marko Djurica/Reuters)

In this picture taken on Thursday, December 1, 2016, an Iranian woman covers herself with a blanket due to the cold, while visiting Khour salt lake during her tour of the Mesr desert about 305 miles (500 kilometers) southeast of the capital Tehran, Iran. Deserts make up parts of Iran which have recently become tourist destination for young Iranians looking for a break on their weekend. The increase in tourists to the desert has stimulated economic growth in the area. (Photo by Ebrahim Noroozi/AP Photo)

Smoke rises from the sauna as Eda Veeroja walks past with birch twigs at Mooska farm near the village of Haanja December 20, 2014. Smoke saunas are usually built without chimney and have a stove that rest on boulders where firewood is burnt until the room heats up. When the smoke is gone and the room reaches the right temperature, people sit inside and whisk each other with birch twigs. The tradition of the smoke sauna in Voromaa vicinity, in the south of Estonia, is enlisted in the UNESCO representative list of the intangible cultural heritage of humanity. (Photo by Ints Kalnins/Reuters)

In this photo taken Saturday, January 24, 2015, a child makes a face while having her photo taken with the snow covered slopes of the Nanshan ski resort behind her in Beijing. As Beijing makes a final push in its bid for the 2022 Winter Olympics, Chinese President Xi Jinping says winning the bid will encourage over 300 million Chinese to take up winter sports by 2022, according to state-run Xinhua News agency. (Photo by Ng Han Guan/AP Photo)

Recycling artist Nicolas Gomez checks the strings of a cello he has made out of an oil barrel for the Orchestra of Recycled Instruments of Cateura, in Cateura, Paraguay February 13, 2015. Saudi Arabia's oil exports have risen in February in response to stronger demand from customers. As OPEC's top producer battles for market share Reuters photographers around the globe have been photographing oil barrels to document how they are utilised once the fuel has been used. (Photo by Jorge Adorno/Reuters)