Many Americans think of school shootings as mass casualty events involving an adolescent with an assault-style weapon. But a new study says that most recent school shootings orchestrated by teenagers do not fit that image — and they are often related to community violence.

The study, published Monday in the journal JAMA Pediatrics, analyzed 253 school shootings carried out by 262 adolescents in the US between 1990 and 2016.

It found that these adolescents were responsible for only a handful of mass casualty shootings, defined as those involving four or more gunshot fatalities. About half of the shootings analyzed — 119 — involved at least one death. Among the events, seven killed four or more people.

A majority of the shootings analyzed also involved handguns rather than assault rifles or shotguns, and they were often the result of “interpersonal disputes,” according to the researchers from University of South Carolina and University of Florida.