The Newtown Police Department was notified of Adam Lanza's intentions to kill students at Sandy Hook Elementary School four years before Lanza killed 20 children, according to the New York Daily News.

Why it matters: The Daily News reports that a man told NPD of Lanza's plans, but the police "said they couldn't do anything, given Lanza's mother Nancy Lanza legally purchased the guns." The FBI said Lanza "engaged in careful, methodical planning and preparation" when he killed his mother, six Sandy Hook staff members, 20 children, and finally, himself.