Robin Williams touched the lives of both humans and animals. Koko, a 43-year-old female gorilla — who once formed a bond with the Oscar-winning actor — mourned the loss of Williams like so many others this week. 

Williams was introduced to Koko when he visited the Gorilla Foundation in Northern California back in 2001. As seen in a reposted video by the organization, the two laughed and hugged during Williams' visit. Recalling that encounter, Koko became visibly emotional once learning that Williams had passed away on Monday, Aug. 11.

"More phone calls about the news came in, and Koko overheard one from a former colleague," Dr. Penny Patterson, her mentor and surrogate mother, noted on on Monday. "About a half an hour later, Koko signed to Penny: 'CRY LIP.'" Koko then "became very somber, with her head bowed and her lip quivering." (Koko is able to understand more than 1,000 signs in American Sign Language.) 

Williams died at the age of 63 from suicide. Fans, costars, and loved ones immediately paid their respects via social media and acknowledged how the star kept them laughing since childhood — on and off screen. Koko was no different. According to Patterson, Koko smiled for the first time in six months while interacting with Williams 13 years ago. (Her gorilla companion, Michael, had recently passed away at the time.)

"But not only did Robin cheer up Koko, the effect was mutual, and Robin seemed transformed," Patterson noted on "From a high-energy entertainer, into a mellow, sensitive, empathetic guy, who also happened to be really funny."

Watch Williams and Koko's 2001 encounter now.