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)

A wolf looks into the camera at the 30 km (19 miles) exclusion zone around the Chernobyl nuclear reactor in the abandoned village of Orevichi, Belarus, March 2, 2016. What happens to the environment when humans disappear? Thirty years after the Chernobyl nuclear disaster, booming populations of wolf, elk and other wildlife in the vast contaminated zone in Belarus and Ukraine provide a clue. (Photo by Vasily Fedosenko/Reuters)

A replica of the bust of Nefertiti stands in the Replica Workshop of the National Museum of Berlin in Berlin, October 2, 2015. The workshop plans to produce 10 to 20 replicas a year, which like the original are made of a limestone core with gypsum finish. Each one will cost 8,900 euros (9,934 US Dollars). (Photo by Axel Schmidt/Reuters)

South Korean actress singers Tiffany (R) and Seohyun react in front of an official camera on the red carpet during 2015 Mnet Asian Music Awards (MAMA) in Hong Kong, China December 2, 2015. (Photo by Bobby Yip/Reuters)

Curator Anna Reynolds with a doll called Pamela and a toy horse on wheels at the launch of the summer exhibition Royal Childhood at Buckingham Palace, London, which celebrates royal childhood with toys and family gifts belonging to the royal children when they were growing up, on April 2, 2014. (Photo by Sean Dempsey/PA Wire)

Afghanistan's interior ministry special forces demonstrate their skills during a military exercise in Kabul, Afghanistan, Thursday, April 2, 2015. Afghanistan's security forces took over full responsibility for the country's security on January 1, 2015. (Photo by Massoud Hossaini/AP Photo)

An young Indian Jain devotee dressed as Lord Krishna participates in a religious rally organised on the occasion of Mahavir Jayanti in Kolkata on April 2, 2015. The most important religious holiday in Jainism, Mahavir Jayanti celebrates the birth of Mahavira, the last Tirthankara, which is generally accepted as 599 BCE. (Photo by Dibyangshu Sarkar/AFP Photo)