Witnessed reports of sudden death are rare, but critical to deciphering its mechanism(s). We report such a death in a seemingly healthy 8-month-old boy in whom seizures and respiratory distress in the prone position were witnessed upon discovery during a sleep period. Following cardiopulmonary resuscitation, anoxic encephalopathy resulted in "brain death" and withdrawal of life support after 2 days. The autopsy did not reveal a primary anatomic cause of death. Metabolic evaluation failed to uncover an inborn error of ammonia, amino, organic, or fatty acid metabolism. Seizures in this case may have been secondary to cerebral hypoxia-ischemia complicating cardiorespiratory arrest of unknown etiology. Yet, they may represent the first manifestation of idiopathic epilepsy, triggering cardiopulmonary arrest, analogous to the terminal events postulated in sudden and unexplained death in epilepsy. This report alerts the forensic community to the possibility that sudden and unexplained death in infants may be due to seizures.