Jamilia Land was 10 when an Oakland police officer pointed a gun at her and ordered her to shut up. “When he did that, my father damn near lost his mind,” Ms. Land recalls of the long-ago incident. She had witnessed the officer harassing her father. Once his ire turned on her, a tussle ensued between the two men and her father, Willie Elvin Land, was beaten with a baton. “I remember how traumatic it was, seeing my father lay there on the ground just helpless and afraid,” she said. “That was the first time I had seen my father afraid. … It changed me.”