To evaluate the efficacy of the IBM protocol we have developed in reducing anger and suicide risk, we will conduct a three-arm randomized controlled trial over the internet. Military veterans and non-veteran community participants reporting elevated trait anger (N = 120) will be randomized to one of three conditions: 1) IBM; 2) progressive muscle relaxation (PMR); or 3) healthy education videos (control). Each condition will consist of eight 15-minute treatment sessions. Participants will complete two sessions per week for four weeks and will be administered assessments at pre- and post-treatment. IBM and PMR conditions will also complete 3-month and 6-month follow-up assessments. To ensure an adequate test of the effects of this intervention on suicide risk, we will oversample for individuals with current suicidal ideation. We hypothesize that: 1) IBM will lead to greater reductions in anger than PMR and control conditions in a sample with problematic anger; 2) IBM will lead to greater reductions in suicidal ideation, perceived burdensomeness, and thwarted belongingness than PMR and control conditions; 3) efficacy of the IBM condition in reducing suicidal ideation will be mediated by reductions in perceived burdensomeness and thwarted belongingness; 4) group differences between IBM and PMR will be maintained at the 3-month and 6-month follow-up assessments.