The Santa Barbara Zoo had to euthanize one of its most beloved and oldest residents, a 47-year-old Asian elephant named Sujatha, officials said Wednesday.

Sujatha was euthanized in her enclosure on Tuesday surrounded by her caretakers at the zoo.

CEO Rich Block said in a video posted on Twitter that Sujatha’s death “is perhaps the most difficult moment” in his 20 years at the facility.

“And I know for the people that care for the elephants this may be the toughest moment in their entire career,” Block said. “There is no way to describe the sadness that is felt.”

Sujatha had been in declining health for the past few years but was able to live comfortably with treatment, Block said. Her well-being declined precipitously in the past couple weeks and she stopped responding to treatment, he said.

Sujatha and her female companion, Little Mac, arrived at the zoo from India in 1972, when they were just 1½ years old, and they’ve lived together ever since.

After Sujatha was euthanized, zoo officials say they allowed Little Mac to visit her in hopes of helping the grieving process.

Zoo officials say elephants are known to grieve for their companions and that if Little Mac is too distressed about losing her best friend or would like to be around other elephants, she could be moved to another facility.

“From 1972 until last night, they were together,” Block said. “Best friends is probably a good way to categorize it. These were two remarkable animals.”

Block praised Sujatha and Little Mac for being “ambassadors for Asian elephants in Santa Barbara for 46 years.”

“Children who first met them in the 1970s have brought their own children, and some even their grandchildren, to meet these wonderful creatures,” Block said in a statement. “We are grateful to Sujatha and Little Mac for how they have enriched all our lives.”