The documentary “Tower” revisits the day Charles Whitman ascended UT-Austin’s iconic tower and unleashed a shooting spree that left 14 dead and more than 30 injured on the mall below. The film airs on PBS stations tomorrow night. Pete Blair, executive director of the Advanced Law Enforcement Rapid Response Training (ALERRT) Center at Texas State University joins us to talk about how the authorities handle active shooter situations. And we’ll also talk with “Tower” director Keith Maitland and Claire Wilson, who was struck by one of Whitman’s bullets.