Police walk past a burning car during riots in Birmingham City Centre on August 8, 2011 in Birmingham, England. After three nights of rioting and looting in and around London, the chaos is starting to spread to other cities around Britain. (Photo by Jeff J Mitchell/Getty Images)

A member of the Fuerza Civil (Civil Force) police unit takes part in a simulated crime situation during a media presentation to show the police model that the federal government wants for the rest of the country, at the police academy in Monterrey December 17, 2014. Fuerza Civil, a tactical team of the police unit trained by the army, was created by the Nuevo Leon government in 2011 to curb down corruption and infiltration by drug gangs in the police corps, local media reported. Promising a new law to stop the infiltration of local governments by organized crime, President Enrique Pena Nieto pledged to reform the penal system and send an proposal to Congress to unify multi-layered police forces in Mexico's 31 states. (Photo by Daniel Becerril/Reuters)

Mounted cop in action on Tremont Street in Boston, Massachusetts, 1920 – 1929 (approximate). (Photo by Leslie Jones)

In this photo taken Tuesday, April 14, 2015, immigrant men armed with machetes make their way onto a Durban, South Africa, street during clashes with police and in search of locals that attacked foreign shop owners in the city center. (Photo by Tebogo Letsie/AP Photo)

Members of the public continue to pay their respects at the scene of a hit and run following civil disturbances in the Winson Green area on August 12, 2011 in Birmingham, England. Police are continuing investigations after three people – reportedly trying to protect shops from rioting and looting in Dudley Road – were struck by a car and killed during rioting. Police have so far arrested over 1,000 people following rioting which erupted over a four-day period across the UK. (Photo by Jeff J Mitchell/Getty Images)

Two girls are detained outside the Currys electrical store in Brixton on August 8, 2011 in London, England. Widespread rioting and looting took place across many parts of London in the early hours of Monday morning in a reaction to earlier rioting in Tottenham in North London. Major disturbances broke out late on Saturday night in Tottenham and the surrounding area after the killing of Mark Duggan, 29 and a father-of-four, by armed police in an attempted arrest on August 4. (Photo by Dan Kitwood/Getty Images)

A policeman is pictured near a woman with a baby during an operation against drug dealers in Cidade de Deus or City of God slum in Rio de Janeiro, Brazil, November 23, 2016. (Photo by Ricardo Moraes/Reuters)

An elephant is used to demolish a house during an eviction drive inside Amchang Wildlife Sanctuary on the outskirts of Gauhati, Assam, India, Monday, November 27, 2017. Indian police on Monday took the unusual step of using elephants in an attempt to evict hundreds of people living illegally in the protected forest area in the country's remote northeast. Police used bulldozers and the elephants in a show of force, and the forest dwellers responded by hurling rocks. (Photo by Anupam Nath/AP Photo)