What makes Starr eventually act? What is her message to the crowd?

After a radio program announces that the grand jury decided not to indict Officer Cruise, Starr gets angry that, after all her efforts, she was unable to get justice for Khalil. She decides that she wants to protest and riot—since the police don’t care about her, she doesn’t care about the police.

When Starr and the others arrive on Carnation, the street where Khalil was shot, Starr sees Ms. Ofrah leading protest chants from the top of a patrol car. Ms. Ofrah is surprised to Starr out on the street. When Starr explains that she’s fed up and wants to protest, Ms. Ofrah asks Starr to fire her so if her parents find out that she helped Starr protest, she wasn’t acting as her attorney but as an activist. Then she hands Starr a bullhorn.

From the top of the police car, Starr speaks passionately to the crowd about the wrongness of Khalil’s death. She leads a chant, “Khalil lived!” before the police throw a can of tear gas at her. She picks up the can and hurls it back towards the police; chaos breaks out on the street.