Instruction? i like the hands on component and doing it makes a lot of sense. reporter: as you ve seen, the training is intense in this room. the trainer knows what he teaches is a sad sign of the times. it s terrible, but i m also glad to do it, oddly enough, because there is something that can be done to help people in those situations. and that s what we re about. reporter: john, the school security industry experts say is a $3.1 billion industry in this country. it s going up every year. brink, who we spent time with in tennessee for the story, today, for example, is with his trainers teaching teachers and administrators this program in minnesota. he says he s had this company for six years, and he s never been busier than he is today. so smart, so practical, but so chilling. so chilling. what a report. thank you so much. we ll be right back.