that there is no ability to effectively prevent all of them. some will occur. the idea whether in the building, just as easy to sit outside the building and wait for school dismissal town where hundreds and thousands of these kids gather around school buses and actually the school. even preventing people from getting into the school, twice a day, hundreds of thousands of kids entering and exiting. how do you start to protect the perimeter? we learn from each one of these. each of these is a learning experience, but reality is, this is a reality that we re going to have more and more of these. bill bratton. former commissioner here in new york, and also, of course, out west and in boston. commissioner, thank you for your insight. we re going to go now to a reporter on the ground there. this is a reporter who is with our affiliate kprc, roseanne