Chris Squire, co-founder and bassist for legendary progressive rock group Yes, has died, according to his bandmate Geoff Downes on Twitter. He was 67. Squire had announced a hiatus from the band in May, following a diagnosis of acute erythroid leukemia.

“Utterly devastated beyond words to have to report the sad news of the passing of my dear friend, bandmate and inspiration Chris Squire,” said Downes. Squire was the only constant member of the band since forming in London in 1968.

Yes released a statement that marks Squire’s sad passing:

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 in Phoenix Arizona, in the arms of his loving wife Scotty.

For the entirety of Yes’ existence, Chris was the band’s linchpin and, in so many ways, the glue that held it together over all these years. Because of his phenomenal bass-playing prowess, Chris influenced countless bassists around the world, including many of today’s well-known artists. Chris was also a fantastic songwriter, having written and co-written much of Yes’ most endearing music, as well as his solo album, Fish Out of Water.

Outside of Yes, Chris was a loving h usband to Scotty and father to Carmen, Chandrika, Camille, Cameron, and Xilan. With his gentle, easy-going nature, Chris was a great friend of many … including each of us. But he wasn’t merely our friend: he was also part of our family and we shall forever love and miss him.

Billy Sherwood, a ’90s-era contributor, has already been announced as Squire’s replacement on the upcoming Yes tour. The band's Aug. 7 concert with Toto will be their first-ever without him.

Chris Squire – "Hold Out Your Hand" (Live at Bass Player Live! in 2012)