Stand off between Police and protesters in Hong Kong

The video captures a tense standoff between police and protesters, with tear gas and rubber bullets being used. Protesters are seen throwing bricks and possibly corrosive substances from balconies, aggravating the police. The unrest is widespread across the city, with warnings of potential terrorist attacks. The day is marked as significant by anti-Beijing protesters, referred to as the 'day of grief'. The situation is expected to escalate further.

How do the protesters feel about the situation according to the text?

What is the significance of the day referred to as 'the day of grief'?