SAN DIEGO (KSWB) – A 6-year-old female orca unexpectedly died Thursday at SeaWorld San Diego after showing signs of illness the day before, the park said.

The cause of death of the killer whale called Amaya will not be known for several weeks after a post-mortem examination is complete, SeaWorld San Diego said in a statement.

“The entire SeaWorld family is saddened by the loss,” the statement reads in part. A spokesperson added that the animal died “with her animal care specialists by her side.”

“Amaya began showing signs of illness on August 18, and animal care specialists and veterinarians began treating her immediately,” the park explained. “Despite her care team’s efforts, Amaya’s condition continued to decline rapidly. Her death was sudden and unexpected.

“This is a very difficult time for those who knew and loved Amaya. She inspired millions of guests to appreciate and learn more about this amazing species. The specialists who cared for her at SeaWorld are heartbroken.”

Nearly a decade ago, SeaWorld faced intense criticism after the release of a book titled “Death at SeaWorld: Shamu and the Dark Side of Killer Whales in Captivity,” and a 2013 documentary titled, “Blackfish.” Those popular features led SeaWorld’s operators to promise to change practices and focus the shows on understanding the animals rather than creating a spectacle.