Family, friends, celebrities, and even ordinary people have expressed their grief over beloved actor and comedian Robin William's passing, but one of the more special friends to mourn his death is in fact a gorilla named Koko.

Reports on Wednesday stated that Koko the Gorilla was mourning William's death after she overheard her surrogate mother and mentor, Dr. Penny Patterson talking over the phone about the actor's passing.

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Koko signed 'CRY LIP' (LIP means woman) after Patterson's colleague stated to cry over the phone while talking about Williams, she added.

Patterson then posted on Koko.org how the gorilla had become extremely sad and was clearly bereaved over the loss of her cherished friend.

Patterson wrote that Koko became very somber throughout the day and sat with her head bowed and quivering lips.

As an Ambassador for Great Ape conservation, Robin Williams met Koko, a gorilla fluent in American Sign Language, in 2001.

During their first meeting, Koko and the actor immediately forged a special bond which was captured on a video from the Gorilla Foundation.

Patterson wrote a tribute post for Williams praising the actor for his ability to simply 'hang out' with Koko and forge a fast and "extraordinary" friendship.

As an introductory statement for the video, Williams explained how he had a "mind-altering experience communicating with a gorilla" citing that they shared an extraordinary experience as the gorilla expressed her thoughts and feelings about things like "daily events, life, love, even death."

Koko and Williams seemed to be genuinely happy with each other's company and even tickled on another like long-time buddies.

Before the end of their encounter, Koko kissed Williams' hand and hugged him.

In the tribute post, Patterson stressed Williams' contribution to the Gorilla Foundation dubbing him as "one of the most powerful ambassadors for great ape conservation."

TagsKoko the Gorilla, Robin Williams, ape mourns williams' death, koko and robin williams, koko