This reddit thread has a lot of info about it too: https://www.reddit.com/r/worldnews/comments/c7sk4g/hong_kongs_legislative_council_is_stormed_by/

Hopefully China doesn't react unintelligently. If they try another Tienanmen Square, it will not end well. I don't know why they can't just wait until 2049 like they agreed upon, they are trying to force the issue in the worst way possible, now something like 25% of Hong Kong is protesting.

For the Chinese government, this is a lose-lose. If they give in, then they will have tons of protests all over China to deal with, of people trying to do the same. If they do nothing, the protests keep getting worse and worse and they might actually lose control of Hong Kong permanently. Although they'd probably go to war before they'd let that happen, but that would destroy their credibility on the world stage, which would result in sanctions by many countries, which would destroy their trade, and thus their economy.

The Chinese govt has to tread very, very lightly. They've put themselves in quite a bad position.