Ruptured aortic aneurysms often present with sudden death, and have varied signs and symptoms depending on the site of rupture and hemorrhage. We report a case of an aortic aneurysm with an aorto-esophageal fistula, which showed slow gastrointestinal bleeding for days before death. A 79-year-old male was brought to a hospital emergency unit, with a history of melena for about 3 days, and recent hematemesis. He collapsed immediately after endoscopy and died. A forensic autopsy which was performed due to possible medical malpractice demonstrated a large saccular aneurysm of the descending thoracic aorta with a fistula into the esophagus. A significant finding was a lid or valve shaped thrombus covering the aortic orifice of the fistula, which may have partly contributed to slow bleeding, and which may have been dislodged by endoscopy. This case suggests that very careful management of aorto-esophageal fistula is needed in patients with clinical signs of possible thoracic aortic aneurysm with slow hemorrhage.