From the Executive Summary: "Ensuring the safety of children at school is a responsibility that belongs to everyone, including law enforcement, school staff, mental health practitioners, government officials, and members of the general public. To aid in these efforts, the U.S. Secret Service National Threat Assessment Center (NTAC) studied 41 incidents of targeted school violence that occurred at K-12 schools in the United States from 2008 to 2017. This report builds on 20 years of NTAC research and guidance in the field of threat assessment by offering an in-depth analysis of the motives, behaviors, and situational factors of the attackers, as well as the tactics, resolutions, and other operationally-relevant details of the attacks. The analysis suggests that many of these tragedies could have been prevented, and supports the importance of schools establishing comprehensive targeted violence prevention programs as recommended by the Secret Service in 'Enhancing School Safety Using a Threat Assessment Model: An Operational Guide for Preventing Targeted School Violence.' This approach is intended to identify students of concern, assess their risk for engaging in violence or other harmful activities, and implement intervention strategies to manage that risk. The threshold for intervention should be low, so that schools can identify students in distress before their behavior escalates to the level of eliciting concerns about safety."