Secondary school students wearing masks join a human chain protesting against what they say is police brutality against protesters, after clashes at Wan Chai district in Hong Kong, China September 9, 2019. Hundreds of secondary school students, many wearing masks with their uniforms, formed human chains in districts across Hong Kong on Monday in support of anti-government protesters after another weekend of clashes in the Chinese-ruled city. REUTERS/Amr Abdallah Dalsh

Secondary school students shout slogans as they form a human chain demonstrating against what they say is police brutality against protesters, after clashes at Wan Chai district in Hong Kong, China September 9, 2019. Hundreds of secondary school students, many wearing masks with their uniforms, formed human chains in districts across Hong Kong on Monday in support of anti-government protesters after another weekend of clashes in the Chinese-ruled city. REUTERS/Amr Abdallah Dalsh

Secondary school students hold a Mickey Mouse stuffed doll with an eye patch as they form a human chain during a protest against what they say is police brutality against protesters, after clashes at Wan Chai district in Hong Kong, China September 9, 2019. Hundreds of secondary school students, many wearing masks with their uniforms, formed human chains in districts across Hong Kong on Monday in support of anti-government protesters after another weekend of clashes in the Chinese-ruled city. REUTERS/Amr Abdallah Dalsh

A secondary school student shouts slogans as he joins a human chain demonstrating against what the students say is police brutality against protesters, after clashes at Wan Chai district in Hong Kong, China September 9, 2019. Hundreds of secondary school students, many wearing masks with their uniforms, formed human chains in districts across Hong Kong on Monday in support of anti-government protesters after another weekend of clashes in the Chinese-ruled city. REUTERS/Amr Abdallah Dalsh

Activists join secondary schools students as they form a human chain demonstrating against what they say is police brutality against protesters, after clashes at Wan Chai district in Hong Kong, China September 9, 2019. Hundreds of secondary school students, many wearing masks with their uniforms, formed human chains in districts across Hong Kong on Monday in support of anti-government protesters after another weekend of clashes in the Chinese-ruled city. REUTERS/Amr Abdallah Dalsh

Secondary school students form a human chain as they demonstrate against what they say is police brutality against protesters, after clashes at Wan Chai district, in Hong Kong, China September 9, 2019. Hundreds of secondary school students, many wearing masks with their uniforms, formed human chains in districts across Hong Kong on Monday in support of anti-government protesters after another weekend of clashes in the Chinese-ruled city. REUTERS/Amr Abdallah Dalsh