Mass Shootings in the United States: Statistical Threat Assessment
According to the Secret Service National Threat Assessment Center, mass shooters over the last decade have had some common traits.
Most of the attackers had exhibited behavior that elicited concern in family members, friends, neighbors, classmates, coworkers, and others, and in many cases, those individuals feared for the safety of themselves or others as a result.
Many of the attackers had a history of physically aggressive or intimidating behaviors, such as history of violent criminal arrests or charges, domestic violence, or other acts of violence towards others.
Half were motivated by specific grievances, and were retaliating for perceived wrongs.
One quarter of the attackers subscribed to conspiratorial or hateful belief systems, including but not limited to extreme misogynistic beliefs, anti-semitic beliefs, or anti-government beliefs.
One quarter of attackers were found to have conveyed concerning communications on the internet, such as threats of harm to others or self, references to previous mass shootings, suicidal ideations, violent content, or hateful rhetoric towards a particular ethnic group.
58% of attackers experienced mental health symptoms prior to or during the attack including depression, suicidal thoughts, and psychotic symptoms. Age of onset varied. 26% demonstrated or expressed concern over their mental health.
34% experienced symptoms of depression and 25% had suicidal thoughts prior to the attacks. Insomnia, social isolation, performance declines, loss or gain of weight, were also reported.
28% experienced psychotic symptoms including paranoia, delusions, and hallucinations.
32% had received some sort of mental health treatment. 24% were formally diagnosed with a mental health condition.
28% of attackers shared final communications before their attack, including calling people to say goodbye, authoring suicide notes, and posting manifestos online. Thirteen attackers made communications indicating an attack was imminent, and 18 engaged in final acts such as selling or giving away their possessions, cancelling a cable subscription, or transferring property to family members.
Just over 10% of attacks were chosen to occur on dates that held some meaning like a holiday, public event, or was personally meaningful to the attacker.
38% of attacks ended quickly within 1 minute, 26% lasted over 15 minutes, while the rest fell in between.
69% of attacks took place in a freely accessible public location; 34% occured in semi public spaces like work places, schools, and houses of worship. 51% of attacks were inside of businesses, and 35% were in open, outdoor spaces.
53% of attackers had no known affiliation with the location of the attack. Some appeared to fire in random locations while others selected specific targets. In the remaining 47% of cases, the perpetrator had an affiliation with the site of the attack, most commonly as a current or former employee, customer, or client.
68% of attacks appeared to target random individuals unknown to them, though in some cases this targeting was based on other factors such as race, religion, gender, ethnicity, or membership with a specific group like homeless people or police officers. One attacker targeted random couples at an outdoor shopping mall because he was frustrated by his inability to find a romantic partner.
In the remaining 32% of attacks, the attackers had one or more specific targets in mind. In nearly all of these attacks, the attack was motivated by a grievance related to either a personal, domestic, or workplace situation. In nearly all of these attacks at least one specific target was harmed, and in most, at least one random victim was harmed as well. Some attackers targeted people connected to these people, such as new boyfriends, an ex wife’s divorce attorney, or their in laws. Other targets included neighbors and bullies.
22% of the time attacks are halted by law enforcement intervention. 10% of the time they are stopped by bystander intervention, and 11% of the time when their weapon became inoperable.
The NTAC identified as many as three or more components to attackers motives:
Specific personal grievances (51%)
Ideological, bias, or partisan based beliefs (18%)
Psychotic symptoms (14%)
Desire to Kill (7%)
Fame or notoriety (6%)
73% of attacks involved firearms, 16% involved knives, 10% involved vehicles, 3% involved blunt objects, 2% involved explosives, and 2% involved arson or incendiary devices. 14 attacks involved multiple weapons, and 21% of attackers brought additional weapons to the attack that were not used, including firearms, knives, and pipe bombs. In some cases, attackers acquired weapons at the site of the attack.
74% of firearm attacks were with handguns, and 32% with long guns. In 16 attacks both handguns and long guns were used. Most attacks involved a semi automatic pistol but 10 were with revolvers. Of the long guns, 33 were semi automatic, 8 were shot guns, and one case involved a firearm capable of fully automatic fire. In 27 cases the firearms were modified including with laser sight, bump stock, suppressor, high capacity magazines, slings or bipods, shortened barrels, or stock handles.
The most frequent caliber used was 9mm (29%)
56% of the attackers owned at least one of the firearms they used. 9% were stolen. 6 involved online communications to facilitate the acquisition of firearms or magazines. In 23% of cases at least one firearm was acquired illegally. 10% previously had firearms confiscated or weapons licenses or permits revoked, or were required to relinquish weapons to law enforcement. Some attackers refused to comply with past orders to surrender weapons.
Most attackers brought items besides their weapons. 34% brought extra ammunition, armored vests, binoculars, eye and ear protection, handcuffs, tactical clothing, and in one instance sewed handcuff keys into their underwear prior to the attack. In 25% of cases attackers brought excess ammunition, ranging from 100 to over 1000 extra rounds. One attacker brought over 5,280 rounds.
96% of mass shooters are male. 47% are white not hispanic, 23% are hispanic, 34% are black, 4% are Asian, 1% are American Indian, 1% are multi racial, and 3% are undetermined.
32% of attackers were known to be employed at the time of the attack; 21% were known to be unemployed. The remaining attackers employment status is unknown.
29% of attackers experienced a job loss prior to the attack, most within five years, some within 1 month. For three attackers, employment ended the same day the attack happened.
64% of attackers had a prior criminal history. 57% had non violent criminal pasts, 38% faced prior charges for violent offenses, and 6% had priors for sex crimes. Non violent crimes included drug, property crime, weapons offenses, conduct crimes, and crimes against persons.
49% had criminal histories that began over five years prior to the attack, 41% faced at least one charge within five years, and 19% within one year. Two were arrested the week prior to the attack.
31% had at least one contact with law enforcement that did not result in arrest. 12% of these contacts were identified prior to their attacks.
34% have a history of illicit drug use, and 12% were under the influence at the time of their attacks.
3% became radicalized in their beliefs via the internet.
19% displayed misogynistic behavior including calling women derogatory names, sexual harassment, threats of sexual violence, or actual secxual assault.
29% displayed a fixation or intensive preoccupation with a person, activity or belief. The main objects of fixation were a former or current romantic partner, a belief system, personal delusions, and prior mass shootings.
21% had an excessive or inappropriate interest in violence, demonstrated an interest in harming others.
28% demonstrated an interest in careers in law enforcement or the military.
29% were identified as withdrawn, loners, or anti social. 36% had a history of bullying or harassing others.
93% of attackers experienced at least one significant stressor within 5 years of the attack, and 77% within one year. 72% were financially unstable and 39% had unstable housing. 22 were homeless.
46% exhibited behavior changes, most within the last five years. 55% first shared concerning communications more than two years prior to their attack. 77% made concerning communication within 30 days of the attack. 37% shared one the day of the attack.
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