This study compared public mass shooters (n = 171) and active shooters (n = 63) in the United States to the general population, homicide offenders, and people who die by suicide. Comparisons with the general population are the foundation of epidemiological research, and comparisons with homicide offenders and people who die by suicide are helpful because public mass shooters and active shooters always intend to kill and often take their own lives. Findings indicate that public mass shooters were more often male, unmarried, and unemployed than the average American. Active shooters were not significantly different from the general population based on prior felony convictions or pre-existing firearm ownership. Public mass shooters and active shooters appeared more like people who die by suicide than homicide offenders, given their high frequency of premeditation, acting alone, suicidal ideation, and unnatural death. Overall, this suggests that felony histories and firearm ownership may have limited utility for threat assessment, but several suicide prevention strategies might help reduce the prevalence of these attacks.