This chapter examines the cognitive, affective, and situational factors that influence the decision-making processes of those who kill. With little existing research that specifically focuses on homicide offender decision making, this chapter brings together criminological and psychological research on violence-related cognition, affect, and the situational dynamics of violent encounters. The authors make the case for combining these three perspectives in order to better understand decision making and homicide. Four case studies, two cases of homicide and two of sublethal encounters, illuminate offenders’ thoughts and feelings prior to and during the commission of the offense and illustrate the complex interplay of cognitive, affective, and situational factors in lethal and near-lethal events. The chapter concludes with proposed avenues for future research.