It's been three years since George Floyd's murder. Minnesota Attorney General Keith Ellison prosecuted the former police officers who killed Floyd, but accountability and justice is not always found in state-sponsored violence against Black Americans. In his new book, Break the Wheel: Ending the Cycle of Police Violence, Ellison retraces the case. As he tells NPR's Leila Fadel, the book – and his experience – is also proof that systems can change to prevent future tragedies.