Mass Attacks in Public Spaces: 2016 – 2020. National Threat Assessment Center (NTAC). U.S. Secret Service U.S. Department of Homeland Security January 2023. “…The 173 attacks contained in this report impacted a variety of locations, including businesses/workplaces, schools, houses of worship, military bases, nonprofit service providers, residential complexes, public transportation, and open spaces. In many cases, the attacker had a known affiliation with the site of the attack. The analysis is intended to provide critical information to a cross-sector of community organizations that have a role in preventing these types of tragedies. Key findings include:

• Most of the attackers had exhibited behavior that elicited concern in family members, friends, neighbors, classmates, co-workers, and others, and in many cases, those individuals feared for the safety of themselves or others.
• Many attackers had a history of physically aggressive or intimidating behaviors, evidenced by prior violent criminal arrests/charges, domestic violence, or other acts of violence toward others.
• Half of the attackers were motivated by grievances, and were retaliating for perceived wrongs related to personal, domestic, or workplace issues.
• Most of the attackers used firearms, and many of those firearms were possessed illegally at the time of the attack.
• One-quarter of the attackers subscribed to a belief system involving conspiracies or hateful ideologies, including anti-government, anti-Semitic, and misogynistic views.
• Many attackers experienced stressful events across various life domains, including family/romantic relationships, personal issues, employment, and legal issues. In some of these cases, attackers experienced a specific triggering event
  prior to perpetrating the attack.
• Over half of the attackers experienced mental health symptoms prior to or at the time of their attacks, including depression, psychotic symptoms, and suicidal thoughts.”