This study tested whether threat-induced errors in police officers' shooting decisions may be prevented through practice. Using a video-based test, 57 Police officers executed shooting responses against a suspect who rapidly appeared with (shoot) or without (don't shoot) a firearm. Threat was manipulated by switching on (high-threat) or switching off (low-threat) a "shootback canon" that could fire small plastic bullets at the officers. After an initial pretest, officers were divided over four different practice groups and practiced their shooting decisions for three consecutive weeks. Effects of practice were evaluated on a posttest. On the pretest, all groups experienced more anxiety and executed more false-positive responses under high-threat. Despite practice, these effects persisted on the posttest and remained equally strong for all practice groups. It is concluded that the impact of threat on police officers' shooting decisions is robust and may be hard to prevent within the limits of available practice.