The study, published Monday in the journal JAMA Pediatrics, analyzed 253 school shootings executed by 262 adolescents in the country between 1990 and 2016.
The researchers said their objective was to find out what types of firearms are used in school shootings, and how firearms are obtained, because these two topics "have not been well explored" in gun violence research.
Of the 262 shooters aged 19 years old or younger, 51.8 percent procured firearms from their family members or relatives, primarily their parents.About 30 percent of them got a weapon from illegal markets, while 22 percent obtained weapons from friends or acquaintances.
"These findings may significantly influence discussions around gun control policy, particularly in advocating for secure firearm storage to reduce adolescents' access to weapons," said the researchers, adding that it "could benefit public health."
A suspect has been arrested in what police have called the 'hate-motivated' shooting of three Palestinian college students in the US state of Vermont.
Handguns were the most used weapon in school shootings. As for procurement methods, these weapons were most frequently stolen from family members or relatives. Despite the more frequent use of lower to moderately powered firearms in school shootings, the study's results indicated stability in the use of high-powered weapons in adolescent school shootings.
An overwhelming majority of the 262 adolescent shooters were male, with an average age of 16. Of these individuals, 57.8 percent were Black, 27.9 percent were White, 8.6 percent were Hispanic, and 5.7 percent represented other racial or ethnic groups.
The researchers also looked at their economic backgrounds and found about 20 percent of them lived below the poverty line, and about 26 percent of their family members did not have high school diplomas, and 10 percent were unemployed.
The data analyzed in this study were from the American School Shooting Study, which compiles information from open-source materials, such as media and academic reports, court records, and police files. The researchers admitted limitations of the source materials, calling for a standardized national reporting system.