[ This animal could not have possibly felt any real sadness. There are people that might have worked with Williams multiple times 13 years ago that aren’t news level sad. ]
The Animal probably is feeling that the trainer is sad and is somewhat empathizing with them, nothing more.
Now if the trainer dies or like the article said they lost a fellow gorilla playmate, then it would be genuine sadness.
Koko grabbed William Shatner’s balls.