This paper examines student exposure to school shootings in the United States since the 1999 shooting at Columbine High School. We analyze shootings that occurred during school hours on a school day and resulted in a death. These shootings are likely to be uniformly reported and have a greater potential to cause harm -- either directly or indirectly -- to enrolled students. We measure the number and characteristics of children who were exposed to them, along with measures of the economic and social environment in which these shootings occur. We distinguish between indiscriminate shootings, suicides, personal attacks and crime-related shootings. The primary finding of our analysis is the importance of separating these types of shootings. Indiscriminate shootings and suicides more commonly affect white students, schools in more rural locations, and those in locations where incomes are higher. The opposite geographic and socioeconomic patterns are apparent for personal attacks and crime-related shootings. Analyses that ignore these distinctions or focus on a particular type may provide a misleading impression of the nature of school shootings. Policy discussions regarding approaches to reducing school shootings should take these distinctions into account.