To date, there are no evidence-based peer bystander intervention trainings (BIT) aimed at educating peers in school shooting warning behaviors. The purpose of this study was to examine an interactive BIT where peers were taught warning behaviors related to someone planning a school shooting and how to report this information. This training was evaluated against a currently available training method (i.e., PowerPoint presentation based) and a control group to determine the best training approach. College students between 18 and 19 years old (N = 57) completed pre, post, and one-month follow-up assessments. At each timepoint accuracy in detection of warning behaviors, overall willingness to report, attitudes toward reporting, perceived behavioral control (PBC), and intent to report was assessed. A linear regression mixed effects model was performed for each variable of interest. Results indicate that all groups increased in accuracy from preassessment to post assessment, and from preassessment to one-month follow-up for the first accuracy assessment, but not the second. Participants’ willingness to report, attitudes toward reporting, PBC, and intent to report increased between preassessment and post assessment, and preassessment and one-month follow-up. The was a significant interaction effect between time and group for willingness to report and PBC between preassessment and post assessment for the interactive BIT group compared to the control group. The interactive BIT group demonstrated the highest positive attitudes toward reporting compared to the control group between pre and post assessment. For intent to report, the PowerPoint presentation group demonstrated the highest increase in intent to report compared to the interactive BIT group at one-month follow-up. Results indicate the intervention training has potential for educating peers in warning behaviors with modifications. Future research should focus on these modifications.