Back-to-back mass shootings in the U.S. have re-ignited passionate debates about gun control in America. But there are other efforts underway to protect people from gun violence-- like the creation of an intelligent building designed to handle an active shooter situation. Engineers and computer scientists at the University of Southern California are using virtual reality to help them design buildings that can protect its occupants. Elizabeth Lee has more from Los Angeles. WARNING: this story contains graphic video that some viewers may find disturbing.