Immersive extended reality (XR) technologies, including augmented reality (AR), virtual reality, and mixed reality, are transforming the landscape of education and training through experiences that promote skill acquisition and enhance memory retention. These technologies have notably improved decision making and situational awareness in public safety training. Despite the promise of these advancements, XR adoption for emergency response has been slow. This hesitancy can be partially attributed to a lack of guidance for integrating these novel technologies into existing curricula. This work aims to guide instructional designers, curriculum developers, and technologists in seamlessly integrating immersive technologies into public safety training curricula. This work provides a comprehensive account of our collaboration with instructional designers, public safety personnel, and subject matter experts in developing an AR-based training curriculum for the Sort, Assess, Life-saving Interventions, Treatment/Transport triage technique used in mass casualty incidents (MCIs). In addition, we introduce a systematic framework for public safety curriculum development based on the Analyze, Design, Develop, Implement, Evaluate instructional design model. Leveraging a human-centered design approach, we first analyze the necessity for immersive learning in public safety. Next, we identify the obstacles in developing XR training experiences and outline our construct of a training prototype through iterative evaluations based on stakeholder feedback. Finally, we share qualitative insights through iterative evaluations with firefighters and emergency medical technicians performing MCI triage tasks in AR, supplemented by survey questionnaires and semistructured interviews. Our goal is to provide a blueprint for a successful integration of immersive technologies into public safety training curricula.