Lam was one of five people from Causeway Bay Books who disappeared in 2015. He later detailed his detention by Chinese authorities.

Lam, who eventually moved his Causeway Bay Books to Taiwan, was one of five booksellers who disappeared in 2015 and resurfaced across border.

‘I want to express my deepest condolences to his family, friends and all those who care about freedom and democracy in Hong Kong,’ William Lai says in Facebook post.