these are vigils that also function as protests. this one, like many others, seemed to allow anyone to speak over the microphone, which makes sense as one of their main requests is free speech.

she was free to join and voice her disapproval (a minority opinion at these events); the audience was free to boo her, which they did; he was not free to punch her

the woman in the hat is basically questioning all the protesters calling for Xi Jinping to step down, asking who will lead after him, that this is a funeral event, and to only shout slogans for things they can be responsible for, to which the woman with the mask retorts with who is responsible for the ten people that died? (i.e., CCP) allegedly he thought the woman in the mask was speaking the entire time.

some people from the event said online that he was attempting to punch a woman that was speaking against the protests, but accidentally punched the woman next to her. not that it makes it much better. you can see it here: https://youtu.be/lg4k4Qu_njg?t=2156