An open school intercom broadcast to students at Sandy Hook Elementary School the murder of their principal and the terrified cries of other children. It's not clear whether the intercom was turned on purposefully to alert the school's staff to the menace or whether the intercom was on for morning announcements. Either way, it caught the initial moments of Adam Lanza's lethal fury and gave teachers and others life saving moments to lock their doors and try to hide their children.

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