The study compared a number of variables for 71 lone-actor terrorists and 115 mass murderers who acted alone. It found little differentiation between the two types of mass murderers in their socio-demographic profiles. Although both types of offenders committed violent acts that involved highly publicized multiple deaths, the intent differed for their violent acts. Lone terrorists committed their violent acts in expression of and commitment to a political or religious ideology; whereas, the other mass murderers acted out of personal feelings of having been wronged by an individual or group. Their behaviors also differed in the degree to which they interacted with co-conspirators, their antecedent event behaviors, and the degree to which they leaked information about their intent to commit a mass murder event. Notably, lone actor terrorists were significantly more likely to verbalize to friends, families, or a wider audience their intent to commit a mass killing. This suggests the need for more public education about the warning signs of an imminent intent to commit mass murder and the importance of taking these signs seriously and report them. Additional research is recommended on the process of radicalization, the features of attack planning and commission, as well as issues pertinent to de-radicalization and disengagement. Access to the full report is provided from this web page.