A member of the German wireless police picks up signals on the radio equipment he carries on his back, while his colleague takes notes. (Photo by General Photographic Agency/Getty Images). Circa 1925

Two children jumping through a water hydrant's shower on a New York street. They have come from a neighbouring co-educational playgroup organised by the city's Police Department. (Photo by Orlando/Getty Images). 1950

A man carries a smoke flare as far-right activists march during the Gay Pride parade on June 12, 2016 in Kiev. More than 700 gay rights activists marched through central Kiev on June 12 amid a massive police presence for the third such gay pride event in the ex-Soviet country where homophobia remains widespread. The June 12 march was the first ever gay pride rally to be held in central Kiev, prompting an unprecedented security operation with several thousand police and National Guard officers lining the route during the event, which lasted around 20 minutes. (Photo by Yuriy Kirnichny/AFP Photo)

Flames from a burning barricade lit by pro-democracy protesters is reflected in the windows of a passing bus as passengers watch on during a protest gathering in front of Mong Kok police station on September 22, 2019 in Hong Kong, China. Pro-democracy protesters have continued demonstrations across Hong Kong, calling for the city's Chief Executive Carrie Lam to immediately meet the rest of their demands, including an independent inquiry into police brutality, the retraction of the word “riot” to describe the rallies, and genuine universal suffrage, as the territory faces a leadership crisis. (Photo by Chris McGrath/Getty Images)

A protester squirts a water gun at Catalan regional police in full riot gear during a protest over the eviction of squatters earlier in the week from “The Expropriated Bank”, in Barcelona, Spain, May 29, 2016. (Photo by Albert Gea/Reuters)

James Brady and a police officer are seen lying on the ground after being shot while the suspect John Hinckley Jr. is apprehended,at right, moments after the attempted assassination of President Ronald Reagan, Washington, DC, March 30, 1981. (Photo by Dirck Halstead/Getty Images)

In this Thursday, August 11, 2016, photo, the injured are helped after a bomb blast in the southern resort city of Hua Hin, 240 kilometers (150 miles) south of Bangkok, Thailand. Police are investigating a series of bomb blasts in Hua Hin and other cities in Thailand. (Photo by Daily News via AP Photo)

Protesters hold on to each other as they are sprayed with water from police water cannons in Martyr square, downtown Beirut, Lebanon October 8, 2015. Lebanese security forces fired tear gas and water cannons to break up an anti-government protest in Beirut on Thursday, and the country's fractious leaders postponed talks aimed at resolving a political crisis that is feeding public discontent. (Photo by Aziz Taher/Reuters)