Ava DuVernay on Emmett Till

In her film for the Smithsonian's National Museum of African American History and Culture, director Ava DuVernay included the brutal killing of 14-year-old Emmett Till, who was murdered after reportedly whistling at at white woman in 1955. In a conversation with "CBS This Morning" co-host Gayle King, DuVernay explains the powerful influence of Till's death, and draws a comparison to the 2012 shooting death of 17-year-old Trayvon Martin.