Here's Amnesty International's description of the situation, for people looking for explanations that don't come from communist propagandists.
People in Hong Kong are facing violent restrictions on their rights to peaceful assembly and freedom of expression. Write to the government and demand they respect and protect the rights of people in Hong Kong now.
In March this year, the government of Hong Kong proposed a bill that, if passed, would have essentially allow the handover of persons in the territory of Hong Kong to mainland China. Millions of people came out in protest of the proposed changes and since then the bill has been withdrawn. But the people of Hong Kong face the ongoing threats to their rights to peaceful assembly and freedom of expression - and excessive police violence goes unpunished.
Our researchers have documented unnecessary and excessive use of force, including tear gas, batons and other less-lethal weapons, used by police, on the largely peaceful protesters; using vague charges to arrest and prosecute peaceful protesters; retaliatory violence against arrested persons in custody; and polices lack of response when protesters were facing violent attacks by counter-protesters and other people.
This has happened both during the pro-democracy Umbrella Movement in 2014 and the Extradition Bill protests that began in March this year. The Hong Kong authorities have used aggressive policing on occasions when they deem the protests are crossing the red-line. This red line is set by the Chinese government, and includes factors like advocating for democracy, challenging the Chinese government or endangering national sovereignty and security".