National Guardsmen are put through riot training in Boston's Commonwealth Armory on Friday, October 18, 1974. Massachusetts Gov. Francis W. Sargent called up the guard to quell school violence, but the city has been relatively calm and the guard has remained in the armories. (Photo by JWG/AP Photo)

British television actress Tracy Shaw poses during a photoshoot held in 2000, in England. (Photo by Stephen Perry/Getty Images)

This is the moment a dog who had his legs cut off as a punishment, is able to walk again thanks to prosthetic limbs, and being rescued by John and Gill Dalley, a couple who moved to Phuket, Thailand, from Leeds to set up the Soi Dog Foundation, August 1, 2016. (Photo by Caters News Agency)

A young vendor hawks food on a market in Kara in the state of Ogun, on September 23, 2015. Nigeria imposed tight movement restrictions in the restive northeast after Boko Haram bombings that killed more than 100 raised fears of fresh attacks over the Eid al-Adha festival. The military said the use of all vehicles would be banned throughout Borno state during the Muslim festival, which is known as Sallah in Nigeria and marked with two days' public holiday from Thursday. (Photo by Pius Utomi Ekpei/AFP Photo)

Extraordinary images of the cruise ship by Jonathan Danko Kielkowski from his book Concordia, published by White Press. The German photographer swam out to where the ship – which ran aground off Tuscany in 2012 with the loss of 32 lives – is moored. Francesco Schettino, the ship’s captain, was jailed for 16 years over the accident. (Photo by Jonathan Danko Kielkowski)

A police officer lies on the street after being run over by a bus during a protest against the increase in the price of public transport in San Cristobal, Venezuela March 29, 2016. (Photo by Carlos Eduardo Ramirez/Reuters)

Actors portraying "corrupted people" participate in the "Unmask the Corrupt" event, organized by the Transparency International non-governmental organization to create awareness on corruption, in Lima, November 12, 2015. (Photo by Mariana Bazo/Reuters)

A guard dog in the suburbs of Yakutsk, Russia, considered to be the coldest city in the world, January 2014. (Photo by Amos Chapple/REX Features)