Chris Squire, the bassist and co-founder of Yes has died at the age of 67. The news confirmed by his bandmates, Squire revealed earlier this year that he was suffering from a rare form of leukemia called acute erythroid.

The band’s official website posted this statement confirming Squire’s death:

“It’s with the heaviest of hearts and unbearable sadness that we must inform you of the passing of our dear friend and Yes co-founder, Chris Squire. Chris peacefully passed away last night (27 June 2015) in Phoenix, Arizona. We will have more information for you soon. Thankyou for all your heartfelt tributes on Facebook and Twitter. We have set up a tribute page here.”

Squire was born in Kingsbury, just outside of London. Yes formed back in 1968 when singer Jon Anderson and Squire met. The duo starting working together became big after opening for Janis Joplin at London’s Royal Albert Hall. Following that performance, the duo was signed to Atlantic Records. Some of their popular songs include “Yours Is No Disgrace,” “Starship Trooper,” “I’ve Seen All Good People,” and “Owner of a Lonely Heart.”

Following the news of Squire’s death, Anderson wrote the following on his official website:

“Chris was a very special part of my life; we were musical brothers. He was an amazingly unique bass player – very poetic – and had a wonderful knowledge of harmony. We met at a certain time when music was very open, and I feel blessed to have created some wonderful, adventurous, music with him. Chris had such a great sense of humor… he always said he was Darth Vader to my Obi-Wan. I always thought of him as Christopher Robin to my Winnie the Pooh.”

Below are some additional heartfelt tributes from musicians and fans all touched by Squire’s work.

Utterly devastated beyond words to have to report the sad news of the passing of my dear friend, bandmate and inspiration Chris Squire. #yes

— Geoffrey Downes (@asiageoff) June 28, 2015

Thank you for all of the amazing music Chris Squire. You will surely be missed.

— John Petrucci (@JPetrucci) June 28, 2015

RIP Chris Squire, super bassist of Yes. An extremely talented musician's musician who mastered his instrument and took it to new realms.

— Tom Morello (@tmorello) June 28, 2015

R.I.P. and thank you Chris Squire. #ChrisSquire,#yes,

— Joe Satriani (@chickenfootjoe) June 28, 2015

Thank you to #ChrisSquire and @yesofficial for some of the most important music of my life. Sending you light.

— Patricia Arquette (@PattyArquette) June 29, 2015