Hong Kong security chiefs sent some 500 police officers to raid a pro-democracy newspaper Thursday while the editor-in-chief and four other executives were arrested at their homes. Journalists at the Apple Daily livestreamed the 7:30 a.m. raid on Facebook, showing police searching reporters’ computers. According to BBC News, police said that the newspaper had published more than 30 articles calling on foreign countries to impose sanctions on Hong Kong and mainland China.

Dozens of activists have been arrested under a controversial national security law introduced after pro-democracy protests shook the territory, but the BBC said it was the first time journalists had been arrested under the law. Apart from arresting the paper’s editor in chief, Ryan Law, police also froze millions of dollars in assets. Apple Daily’s owner, the pro-democracy billionaire Jimmy Lai, is already in jail.