Not only is the world mourning the loss of comedian Robin Williams, but so is a gorilla.

Koko, a gorilla that knows American Sign Language and understands human language, met Robin Williams in 2001. He helped cheer her up while she mourned the loss of her gorilla friend, Michael, a year earlier. Before she met Williams, she hadn't smiled in more than six months.

Today.com reports Williams and Koko acted like old friends, hugging and tickling each other.

In a post on Koko.org, her handlers say she overheard them talking about Williams' death.

"Koko came to Dr. Patterson with an inquiring look on her face. Dr. Patterson explained that 'we have lost a dear friend, Robin Williams,'" the post said.

By the end of the day Koko became sad, bowing her head with a quivering lip.

Check out video of Koko meeting Williams below:

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