School shootings are one of the most salient social problems in America. Most prior research in this area has focused on identifying their causes and evaluating preventive school safety measures. An overlooked issue involves what to do with individuals who plan, attempt, or commit school shootings. Using data from an experiment embedded in a national survey of American adults (N = 1100), this study seeks to answer that question. We examine the public’s sentencing preferences and perceptions of rehabilitation potential for offenders who plan, attempt, and/or carry out a school shooting. We focus specifically on the effects of offense outcomes and of the shooter’s age and mental health. We find that offense severity is the strongest predictor of both sentencing preferences and perceived rehabilitation potential. Offender age interacts with offense severity, such that sentencing preferences are harsher for adult than juvenile shooters, but only for mid- and high-severity offenses.