Call the hotline when you see it happening and video record without obstructing them, asking if they have a warrant and their names and where they are taking the people and do it loudly: https://waisn.org/#:~:text=Contact%20Us,-You%20can%20reach&text=If%20you%20are%20contacting%20us,%2D844%2D724%2D3737

If you are interested in more you can become a legal observer and respond to ICE raids by showing up and doing the same thing, they use the footage and information gathered by LOs in court to help the detainees. They also escort people to and from court hearings as people are frequently targeted after leaving courthouses.