One-quarter of the attackers studied in 2016 to 2020 were motivated by conspiracy theories or hateful ideologies, but one-quarter of the attackers were based on personal grievances of some sort.
The agency, known for protecting presidents, has set up a National Threat Assessment Center to monitor trends in violence that could threaten the people it protects, as well as the public.
The report details 173 attacks that hurt three or more people in public spaces, including churches and schools, from 2016 to 2020. The trends could help community leaders know what red flags to spot before someone carries out the next mass attack, said Lina Alathari, the chief of the Secret Service's National Threat Assessment Center.
Anti-government, antisemitic or misogynistic ideologies that motivated attackers included anti-government, antisemitic or misogynistic views. Nearly one-third of all attackers had evidence of planning their attacks, according to the authors.
The report says that the typical attacker was a 34-year-old man motivated by personal grievances rather than ideology.
Alathari said the grievances could be perceived wrongs, most often relating to personal issues, maybe health or financial issues, workplace issues, as well as issues with family and romantic partners. Alathari told NBC News that we need to look at how to deal with interpersonal grievances to make sure they don't escalate.
More than three-quarters of all attacks involved firearms, and over 80% of attacks that used guns resulted in at least one death, the report found. The most of the attackers used handguns, but one-third of them used long guns, a category that includes automatic and semi-automatic weapons. In fewer than 50% of attacks, attackers who used weapons other than guns fatally wounded victims.
In more than one-quarter of all mass shootings, the attackers possessed firearms illegally.
Alathari said that communities should take preventative action to make sure that they are not at risk of a tragedy like this one, regardless of whether the trends call for gun reform.