Black Lives Matter activists interrupted former President Bill Clinton during a speech in support of Hillary Clinton in Philadelphia on Thursday—challenging the Clintons on their support for the 1994 crime bill, which led to a massive expansion of incarceration in the United States. Activists shouted, “Black youth are not super predators”—a reference to Hillary Clinton’s 1996 comments about some youth. They also held signs reading “Clinton Crime Bill Destroyed Our Communities.” In response, Bill Clinton defended Hillary Clinton’s use of the term “superpredators” and accused the activists of defending criminals.

Bill Clinton: “Wait, wait. Whoa, whoa. Wait a minute, wait a minute. OK, I heard it. Can I answer? See these other signs? This is what’s a matter. I don’t know how you would characterize the gang leaders who got 13-year-old kids hopped up on crack and sent them out onto the streets to murder other African-American children. Maybe you thought they were good citizens. She didn’t. She didn’t. You are defending the people who killed the lives you say matter.”

This comes as Hillary Clinton is facing an increasingly tough challenge by Bernie Sanders in the New York primary on April 19.