We investigated whether motivated reasoning rooted in partisanship affects the attributions individuals make about violent attackers’ underlying motives and group memberships. Study 1 demonstrated that on the day of the Brexit referendum pro-leavers (vs. pro-remainers) attributed an exculpatory (i.e., mental health) versus condemnatory (i.e., terrorism) motive to the killing of a pro-remain politician. Study 2 demonstrated that pro-immigration (vs. anti-immigration) perceivers in Germany ascribed a mental health (vs. terrorism) motive to a suicide attack by a Syrian refugee, predicting lower endorsement of punitiveness against his group (i.e., refugees) as a whole. Study 3 experimentally manipulated target motives, showing that Americans distanced a politically motivated (vs. mentally ill) violent individual from their in-group and assigned him harsher punishment—patterns most pronounced among high-group identifiers.