The death of George Floyd after a white police officer knelt on his neck for nearly nine minutes was caught on camera by not one, but several witnesses, as they begged officers to let Floyd up. 

"No one in their right mind, regardless of their ethnic identity, could deny that. So that's where surveillance works in our favor," said Theopia Jackson, president of the Association of Black Psychologists.

As hundreds of thousands joined protests against systemic racism and police brutality, law enforcers used powerful surveillance tools to track them.

Drones flew over protests in Minneapolis and New York. Facial recognition software is being used with some police body cameras. Law enforcement can use signals from your cellphone or automatic license plate readers to follow your movements.

"We have to push toward a world where people can feel free to go to protest and express themselves without worrying that they're going to be targeted by surveillance and their identity is going to be revealed or they're going to be retaliated against," said Neema Singh Guliani, senior legislative counsel at the American Civil Liberties Union.

Watch the video to find out how police are tracking protests, how the data is used, and how cameras on so many officers have fundamentally changed the way we protest.