One of the few recurring characteristics in school shooters’ stories is their expression of existential concerns. Many discuss their hatred of the world and existential loneliness in their manifestos, suicide letters, or social media updates. These expressions—called leaking—are made during the planning period preceding their deed. They are not only important in terms of prevention, but also help us understand the intrinsic meanings in this seemingly irrational and psychopathological behavior. This study offers a content analysis of the existential issues in personal expressions of school shooters prior to their deeds in order to shed more light on their motives.