The founding chair and the secretary general of a pro-democracy political party are alerting the world to violent state repression in Hong Kong.
It comes after a new law was brought before National People's Congress in China banning "treason, secession, sedition, and subversion" in Hong Kong.
Demosistō founding chair Nathan Law tweeted that police fired tear gas without any disorder taking place.
"This is the future of Hong Kong under National Security Law: No freedom of assembly and speech," Law declared.
Another Demosistō leader, secretary general Joshua Wong, called on fellow Hong Kong residents to stand up and fight back.
"Time is running out in Hong Kong," Wong tweeted. "We need to try our best to oppose the evil national security law."
There are approximately 300,000 Canadians living in Hong Kong.
The last British governor of Hong Kong, Chris Patten, told the Sunday Times on May 23 that the city's residents have been "betrayed by China".
Under an agreement prior to Britain's 1997 handover, China promised that Hong Kong's autonomy would be preserved under a "one country, two systems" principle.
“What we are seeing is a new Chinese dictatorship,” Patten told the Times. “The British government should make it clear that what we are seeing is a complete destruction of the joint declaration.”