TAIPEI, Taiwan (AP) — The founder of a bookshop specializing in texts critical of China’s Communist Party leaders was attacked with red paint in Taiwan on Tuesday, but suffered no serious physical injuries.

Lam Wing-kee was assaulted by a man wearing a mask and dark clothes while he was sitting alone at a coffee shop. The assailant remains unknown, but surveillance footage provided by the police shows a person fleeing the scene on foot as Lam chased him.

Lam was one of five shareholders and staff at the Causeway Bay Book shop in Hong Kong, which sold books and magazines purporting to tell the inside lives Chinese leaders and scandals surrounding them. He was put into Chinese custody in 2015 and was released on bail and allowed to return to Hong Kong in June 2016.

Lam left Hong Kong for Taiwan last year over extradition fears and has remained outspoken about the diminishing space for free speech in Hong Kong. Although claimed by Beijing as its own territory, self-governing Taiwan has become a safe haven for critics of the Chinese government, with its flourishing democracy and robust defense of civil rights.

Lam raised nearly $200,000 through online fundraising to fund his new bookstore in Taiwan, which he still plans to open on Saturday.