Safety investigations in aviation aim to identify potential root causes. They use structured techniques to analyze information from flight data and cockpit voice recorders. Full-scale medical simulations using audiovisual recordings provide similar possibilities. During a simulated cardiac arrest, an incident related to use of the defibrillator (automated external defibrillator) occurred with emergency medical services (EMS) providers. Treatment interventions and dialogs during the incident were extracted from audiovisual recordings and transferred into a transcript of events.Knowing indicated treatment measures, the team adhered to automated external defibrillator voice prompts rather than follow their own assessment. Cardiopulmonary resuscitation was on hold for 72% of the time. Time to first defibrillation was delayed by 2:17 minutes. Transcript allowed us to identify faulty decision-making, loss of leadership, and automation bias as possible root causes. Use of RCA methodology during medical simulation improves understanding of critical incidents and can contribute to training of EMS personnel and education of instructors.