another student. >> it's hard for people to understand. >> we continue on the story. dale yeager is a forensic profile and safety analyst with seraph corporation. and is the author of the report "sandy hook, lessons learnt", and he joins us tonight. welcome. >> thank you. >> another horrible violent attack at a school. this time with knives. what do you make of this one? >> well, it's another preventible crime. that's what i see after a 25 year career of dealing with columbine, sandy hook. this is just going to continue because we have people who are throwing their hands in the air and wondering why, and ultimately this was a preventible act and questions need to be asked. >> how do you prevent it? >> first of all, the department of education says that in washington you must have