Tomorrow's vigil smacks of the sort of thing which will be crawling with pigs who are eager for a fight, so please familiarise yourself with your rights and this constructive advice from Green and Black Cross if you're going. https://greenandblackcross.org/guides/key-advice/
Key points for safely interacting with the police:
No Comment - you do not have to answer police questions, whether in an "informal chat" or interviewed when arrested. If arrested, you are within your rights to give a prepared statement and then answer "no comment" to everything else.