These HK rioters are getting more violent and aggressive now because their numbers have declined significantly. Thus, they made up their reduction in size with more violent acts. They tried to snatch the police officer's gun and throw molotov cocktails (petrol bombs) directly at the police.
We had stated these intensified acts of violence in our previous post below.
http://sg-stock.blogspot.com/2019/09/my-observations-of-hk-protests.html