A 78-year-old woman during physical exertion suddenly developed abdominal pain accompanied by pallor and a drop in blood pressure to as low as 70/40 mm Hg. Death occurred with signs of acute heart failure. Autopsy detected marked atherosclerosis and a sacculation of vessel wall in the abdominal aorta. The sacculation is 16 cm in diameter and filled with blood clots. In the wall of the sacculation there is a fissured perforation. What pathology occurred in the woman's aorta?