day. the district police chief made the decision to hold officers back from the robb elementary classroom. the shooter locked himself inside. now we know those officers waited for nearly 80 minutes. it was a terrifying nearly hour and a half for the entire school. here is what one teacher told her students to do when she heard the gunfire. she spoke with our ore morgan chesky. i just kept hearing boom, boom, boom. it kept going off for what felt like an eternity. reporter: as the gunman walked towards her school, nicole shouted for her kids to hit the floor seconds before glass shattered her classroom. i had one student laying on top of me, and i had a bunch of other students right over here by me. i just remember praying, please, god, please, god, keep us safe. reporter: she and her students managed to get to safety. when she learned as many as 19 officers waited 47 minutes before engaging the gunman, she said this where do you believe blame should lie? on the pe