Ramu II died of a gastric ulcer. The primary causes are bacterial infection by Helicobacter sp., parasitic infections, high dietary histamine, foreign body ingestion, and stress.
The stress of being removed from his pod, undertaking the furthest transit of any captive Orca and living in a small pool likely all contributed.
Being nine years old he certainly had to have been one of the oldest Orcas ever captured! Most of the time they were individuals around three to four years old as they were more easy going, easier to transport and also less adapted to the ocean in a way.
He was apparently highly aggressive too, and often attacked his trainers.