Most mass attackers exhibited behavior that concerned family members, friends, neighbors, classmates and co-workers prior to taking violent action, according to Mass Attacks in Public Spaces: 2016 to 2020, a comprehensive report released by U.S. Secret Service National Threat Assessment Center (NTAC) that examined 173 incidents of targeted violence and highlighted the observable commonalities among the attackers.
The attacks contained within the report impacted a variety of locations, including businesses and workplaces, schools, houses of worship, military bases, residential complexes and more. In many of these cases, the attackers had a known affiliation with the site of the attack.