This article argues that the organizational structure and culture of schools may impede the prevention of violence in America's schools, specifically threat assessment and management for students of concern. The data come from a qualitative case study of a school shooting where two students died; the data include deposition testimony from 12 school officials and more than 4,000 pages of school and law enforcement records. The findings illustrate the way the school's organizational structure and culture shaped and hindered violence prevention practices. The tightly coupled guidelines for threat assessment created an institutional myth of safety and a false sense of security for the school and district, and the loosely coupled structure of the organization led educators to modify guidelines and make decisions about the student's behavior problems and discipline without consulting others. The school's culture of autonomy for staff and fresh start mentality for students created unintentional secrets about the history of the student's difficulties, which gave educators little context for understanding the problem behaviors they observed and inhibited the threat assessment team's ability to adequately evaluate and monitor those behaviors. Recommendations for building organizational structures and cultures that support violence prevention in schools are discussed.