killed in two days. allegedly by students. i'm about to speak live here in studio with one teacher who was confronted by a 12-year-old in school with a loaded gun. her story, you will never forget. that's coming up. but first, in cases of gun violence, it's tough to train for the unexpected, but in emergency rooms, doctors and nurses are using these high-tech dummies to prepare for saving lives. take a look at this technovation. >> i'm alert. i'm alert. >> two liters of fluid. >> 84/56. >> the sights and sounds of an emergency room. >> how are you feeling? >> conditions that trauma doctors like robert benjamin are trained to handle, but this is not an average work day. >> i had no idea that this was going to be that intense. >> the trauma team is training. their patient is bleeding. and has rapidly changing vital signs. but he's not in danger of dying