A 6-year-old killer whale has passed away suddenly at SeaWorld San Diego

A killer whale at SeaWorld San Diego passed away not long after it started exhibiting signs of illness earlier this week, the theme park said.

The 6-year-old Amaya passed away Thursday but the reason will not be known until the results of a post-mortem exam are finished, and that could be weeks, SeaWorld's statement said, according to the Associated Press.

"Amaya began showing signs of illness on August 18, and animal care specialists and veterinarians began treating her immediately. Despite her care team's efforts, Amaya's condition continued to decline rapidly. Her death was sudden and unexpected," the statement said, according to the AP.

"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 statement noted.

The organization's website indicates that Amaya was the youngest of the orcas, while the oldest is more than 50 years old.

"Amaya, whose name means 'night rain,' is the youngest orca and enjoys spending time with her mother Kalia and father Ulises. Amaya is one of the most playful whales in our pod and loves interacting with her animal care specialists. She has helped us gather and share critical information about calf development for researchers studying wild populations," according to the SeaWorld website.

The organization had announced the end of its killer whale breeding program in March 2016, according to the AP.

The final orca birthed in SeaWorld's former breeding program passed away in 2017 at only 3 months old while it was being treated for infection at SeaWorld's San Antonio park, the outlet noted.