Police killings of individuals with mental illness have prompted calls for greater funding of mental health services to shift responsibilities away from the police. Such investments can reduce police interactions with vulnerable populations but are unlikely to eliminate them entirely, particularly in cases where individuals with mental illness have a weapon or are otherwise dangerous. It remains a pressing question, then, how police should respond to these and other vulnerable aggressors with diminished culpability (VADCs). This article considers and ultimately rejects (...) three potential approaches from the ethics of defensive force literature. It looks to improve on them by developing what I call the fusion account, which explains how vulnerability and diminished culpability fit together to provide moral grounds for extra protections from deadly force. The article’s final sections explore the policy implications of the fusion account for police administrators, officers, and the law. (shrink)