STATEN ISLAND, N.Y. — In most cases, attackers who targeted schools in the United States had a history of school disciplinary actions, exhibited concerning behaviors, and were victims of bullying, which was often observed by others, according to a study released by the U.S. Secret Service.

The Secret Service released the study, “Protecting America’s Schools: A U.S. Secret Service Analysis of Targeted School Violence,” that identifies 41 incidents of attacks against kindergarten through 12th-grade schools in the United States from 2008 to 2017. The findings will help prevention efforts for schools and law enforcement across the country, as communities work to develop threat assessment protocols geared toward preventing school violence tragedies.

“Keeping schools safe requires a team effort, and I am proud to stand with our partners across the federal, state and local governments, our school boards, law enforcement and the public in this important work to better protect our children,” said James M. Murray, U.S. Secret Service director, in a news release. “The Secret Service will steadfastly continue these collaborative efforts in support of our nation’s schools and communities.”

Researchers with the Secret Service National Threat Assessment Center examined the background and behaviors of the attackers.

The study found that all but two of the attacks occurred in public schools, and 73% were carried out at high schools. Most of the schools (80%) implemented some type of physical security measure, and 66% had full- or part-time school resource officers on campus. The most commonly used physical security measure was school lockdown procedures, followed by security cameras at schools and alert systems that notified school community members via text or phone call.

The Secret Service recommends schools implement multidisciplinary school threat assessment teams that will help schools develop the capacity to identify, assess and manage students who are displaying concerning or threatening behaviors.

About 61% of attackers used firearms, and 39% used knives. Attackers were predominantly male (83%), and white (63%). About 17% of attackers were female, 15% were black, 5% were Hispanic. Their ages ranged from 12 to 18, with an average age of 15 years old.

Here are 10 warning signs before a school attack, according to the report.

1. There is no profile of a student attacker or a profile for the type of school targeted.

Attackers varied in age, gender, race, grade level, academic performance and social characteristics. Schools also varied in size, location and teacher-to-pupil ratio. Instead of focusing on a set of traits of characteristics, threat assessment processes should focus on gathering relevant information about a student’s behaviors, situational factors and circumstances to assess risks.

2. Attackers usually had multiple motives, with the most common involving a grievance with classmates.

It’s critical to discover a student’s motive for engaging in concerning behavior to assess the student’s risk of violence. It can allow the threat assessment team to intervene and development strategies to redirect violent choices.

3. Most attackers used firearms, and firearms were most often acquired from the home.

Students can be resourceful in accessing firearms stored in their home. Many attackers used unsecured firearms, and others were able to gain access to firearms in a secured safe. Some students used knives instead of firearms. The threat assessment should explore if a student has access to any weapons, especially those at home.

4. Most attackers had experienced psychological, behavioral or developmental symptoms.

It’s important to ensure students and parents have access to, and are informed about, mental health resources, social services and substance abuse treatment. Many of the attackers in this study had received mental health treatment.

5. Half of the attackers had interests in violence topics.

Half of the attackers in this study displayed unusual or concerning interest in violence of weapons. This should initiate further information gathering, assessment and management by school personnel.

6. All attackers experienced social stressors involving their relationships with peers and/or romantic partners.

Every attacker in the study experienced at least one social stressor, frequently related to bullying. Other stressors included family, academics or school discipline. Schools should adopt and enforce zero-tolerance policies on bullying, and provide students with strategies related to stress management and development of coping skills.

7. Nearly every attackers experienced negative home life factors.

Negative home life factors included parental divorce or separation, drug use or criminal charges among family members, or domestic abuse. Information-sharing among agencies is crucial to address the impact of negative home experiences. Sharing information among schools, law enforcement, social services and courts can ensure students get needed resources.

8. Most attackers were victims of bullying, which was often observed by others.

The study found that in many cases, the school was aware the attacker experienced bullying, but responses to bullying varied. In some cases, the school did little to intervene or intervened in a way that increased bullying of the student. Students should be provided a way to anonymously report concerns without fear of retaliation. Schools should implement comprehensive programs to promote safe and possible school climates while supporting the social and emotional wellbeing of students.

9. Most attackers had a history of school disciplinary actions, and many had prior contact with law enforcement.

Most attackers had a history of receiving school disciplinary actions resulting from a range of inappropriate behavior. Actions included the attacker being suspended, expelled or having law enforcement interactions. Schools should employ disciplinary actions that ensure fairness, transparency with the student and family and appropriate follow-up.

10. All attackers exhibited concerning behaviors. Most elicited concern from others, and most communicated their intent to attack.

The initial indicators of a student in distress or exhibiting concerning behaviors were often observed by peers, school staff, family members or others in the community. The study highlights the importance of encouraging students, school personnel and family members to report troubling or concerning behaviors.