A demonstrator is detained by police officers during a protest in Hong Kong, China on August 31, 2019. Hong Kong police fired tear gas and water cannons and pro-democracy protesters threw petrol bombs in the latest in a series of chaotic clashes that have plunged the Chinese-ruled city into its worst political crisis in decades. (Photo by Kai Pfaffenbach/Reuters)

Demonstrators clash with riot police during a protest against President Sebastian Piñera on October 21, 2019 in Santiago, Chile. President Sebastian Piñera suspended the 3.5% subway fare hike and declared the state of emergency for the first time since the return of democracy in 1990. Protests had begun on Friday and developed into looting and arson, generating chaos in Santiago, Valparaiso and a dozen other cities resulting in at least 8 dead. (Photo by Marcelo Hernandez/Getty Images)

A firefighter uses a saw to open a metal gate while fighting a fire in a convenience store and residence during clashes after the funeral of Freddie Gray in Baltimore, Maryland in the early morning hours of April 28, 2015. (Photo by Eric Thayer/Reuters)

A protester runs from a jet of water shot from a police water cannon in the courtyard of the University of Santiago, during clashes between students and police, in Santiago, Chile, Thursday, May 14, 2015. In the capital and other cities across the country, high school and university students marched, for the second time this year, to demand education reform. (Photo by Luis Hidalgo/AP Photo)

A spectator at the Maslenitsa car battle, reacts during a clash, in the village of Goroshki, some 35 kilometers from Minsk, Belarus, 12 March 2016. The battle which is held at the Historical and Cultural Complex, Stalin line, is a small local competition, with participants from Belarus and Russia. (Photo by Tatyana Zenkovich/EPA)

A demonstrator catches fire after the gas tank of a police motorbike exploded during clashes in a protest against Venezuelan President Nicolas Maduro, in Caracas on May 3, 2017. Venezuela' s angry opposition rallied Wednesday vowing huge street protests against President Nicolas Maduro' s plan to rewrite the constitution and accusing him of dodging elections to cling to power despite deadly unrest. (Photo by Juan Barreto/AFP Photo)

A man lying on the ground is assisted by French policemen during clashes bewteen English and Russian supporters in the Old Port of Marseille, France, Saturday, June 12, 2016, before the UEFA EURO 2016 group B match between England and Russia. (Photo by Daniel Dal Zennaro/ANSA via AP Photo)

A fellow officer comes to the aid of injured patrolman C.V. Satt, who was pelted with rocks and beer bottles during a clash between police and relief demonstrators in Denver September 23, 1935. (Photo by Henry G. Eisenhand/AP Photo)