Sudden cardiac death (SCD) is a rare yet devastating event that can occur in young athletes. Although hypertrophic obstructive cardiomyopathy is the most common cause of SCD, some other genetic abnormalities have been identified as proarrhythmic. However, there is not routine screening for these other genetic abnormalities. Furthermore, consumption of caffeine, stimulant medication, or prolonged exercise can potentiate the underlying arrhythmic potential. In the event of SCD, advanced cardiac life support (ACLS) should be performed immediately and exactly. The authors present a case of an otherwise healthy young male who collapsed during a marathon and could not be resuscitated despite aggressive measures. After aggressive resuscitative efforts, the patient ultimately expired. A postmortem autopsy revealed no cardiac structural abnormalities, and the cause of death was determined to be cardiac arrhythmia of undetermined etiology. Postmortem genetic testing revealed a heterozygous variation in calcium voltage-gated channel auxiliary subunit beta 2 (CACNB2), a gene associated with arrhythmia and calcium channelopathy. Toxicology showed therapeutic levels of amphetamine. This case highlights the eminent risk of cardiac death in young athletes with proarrhythmic genetic variations, especially in the setting of endurance sport.