Another mass shooting in the U.S. This time it's on July 4, Independence Day in the United States. A rooftop shooter opened fire with a high-powered rifle at a parade in Highland Park, killing seven and injuring dozens. 

Leaders and activists are again demanding change. But ironically, the change has already come. Less than two weeks ago, U.S. President Joe Biden signed the most significant firearms legislation in nearly 30 years. Why didn't it stop the shooting?