Author Dave Cullen on lessons learned from Parkland, Columbine in the wake of Uvalde school shooting
March for Our Lives is planning a nationwide protest this June in response to the Uvalde school shooting, roughly four years after the shooting at a high school in Parkland, Florida that killed 17 people. Vanity fair contributor Dave Cullen is the author of best-sellers "Columbine" and "Parkland: Birth of a Movement." He joined CBS News' Anne-Marie Green to discuss the lessons learned from those tragedies.