Koko the gorilla cries in mourning of Robin Williams after bonding with him 13 years ago (Video)

Koko the gorilla, who was befriended by the late Robin Williams in 2001, cried in mourning upon hearing the news that he had passed away this week.

After their first meeting, during which onlookers say they had an instant connection, they filmed a PSA for the ¬Gorilla Foundation in 2004. Koko is known for her ability to communicate through sign language.

The Gorilla Foundation’s president, Dr. Penny Johnson, said Koko knew there was something wrong when Patterson’ received a phone call about Williams’ death.

“After the first call, 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 foundation said in a statement. “Koko was quiet and looked very thoughtful.”

They added, “Koko became very somber, with her head bowed and her lip quivering.”

BuzzFeed reports Koko then signed the words for “woman” and”crying” to Patterson.

Here’s Koko’s tribute to Williams, which includes their first meeting:

image via INFPhoto.com