Charred parts of a burnt wall is seen above a sign of Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 20, 2019.

A statue, decorated with a yellow helmet and mask by anti-government protesters, is surrounded by garbage inside the student union building at the besieged Hong Kong Polytechnic University (PolyU) in Hong Kong, China, November 20, 2019.

A protester walks with a space blanket provided by a medical personnel, in Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 20, 2019.

Graffiti is seen on a wall in Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

A message is written in graffiti on the campus of the Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

A protester looks out from the balcony of the besieged Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

A protester walks on the campus of the Hong Kong Polytechnic University (PolyU), in Hong Kong, China November 21, 2019.

Belongings left behind by anti-government protesters lay on gymnastic mats at a gymnasium that served as sleeping quarters at the Polytechnic University (PolyU) that is surrounded by police, in Hong Kong, China November 21, 2019.

Belongings left behind by anti-government protesters lay on gymnastic mats at a gymnasium that served as sleeping quarters at the Polytechnic University (PolyU) that is surrounded by police, in Hong Kong, China November 21, 2019.

A helmet, gas mask, and sleeping of a protester is left behind in the library of in Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

Belongings left behind by anti-government protesters lay on gymnastic mats at a gymnasium that served as sleeping quarters at the Polytechnic University (PolyU) that is surrounded by police, in Hong Kong, China November 21, 2019.

A protester looks for police as he tries to leave the campus of the Hong Kong Polytechnic University (PolyU), in Hong Kong, China November 19, 2019.

Graffiti and debris are seen in Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 20, 2019.

A yellow helmet lies in a tent left behind by anti-government protesters who were camping overnight on the campus of the besieged Hong Kong Polytechnic University (PolyU) in Hong Kong, China, November 20, 2019.

An area that used to be a protesters' post is seen in Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

Trash is scattered near a former frontline at the besieged Hong Kong Polytechnic University (PolyU) in Hong Kong, China, November 20, 2019.

A chicken is seen among debris at a cafeteria in Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 20, 2019. Picture taken November 20, 2019.

A message is written in graffiti on the campus of the Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

A protester walks in the gymnasium which served as a sleeping area on the campus of the Hong Kong Polytechnic University (PolyU), in Hong Kong, China November 21, 2019.

Belongings left behind by anti-government protesters lay on gymnastic mats at a gymnasium that served as sleeping quarters at the Polytechnic University (PolyU) that is surrounded by police, in Hong Kong, China November 21, 2019.

A message is written in graffiti on the campus of the Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

Books seen littered on the ground inside a library inside the Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

Scattered trays are seen at a cafeteria in Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 20, 2019.

An "SOS" sign written with clothes is seen on the campus of the Hong Kong Polytechnic University (PolyU), in Hong Kong, China November 19, 2019.

A catapult lies on the ground at the besieged Hong Kong Polytechnic University (PolyU) in Hong Kong, China, November 20, 2019.

A message is written in graffiti on the campus of the Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

A message is written in graffiti on the campus of the Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

Clothes are scattered by anti-government protesters on the floor of a gym at the besieged Hong Kong Polytechnic University (PolyU) in Hong Kong, China, November 20, 2019.

A helmet is seen among the remains of a burnt barricade in Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 20, 2019.

A message is written in graffiti on the campus of the Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

A message is written in graffiti on the campus of the Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

Belongings left behind by anti-government protesters lay on gymnastic mats at a gymnasium that served as sleeping quarters at the Polytechnic University (PolyU) that is surrounded by police, in Hong Kong, China November 21, 2019.

Protesters' gear lies on the ground at the campus of the Hong Kong Polytechnic University (PolyU), in Hong Kong, China November 19, 2019.

The slogan "Never Surrender" is spray painted on a wall in the besieged Hong Kong Polytechnic University (PolyU) in Hong Kong, China, November 20, 2019.

Graffiti and debris are seen in Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 20, 2019.

A message is written in graffiti on the campus of the Hong Kong Polytechnic University (PolyU) in Hong Kong, China November 21, 2019.

Belongings left behind by anti-government protesters lay on gymnastic mats at a gymnasium that served as sleeping quarters at the Polytechnic University (PolyU) that is surrounded by police, in Hong Kong, China November 21, 2019.