Peter Tork, a member of the made-for-TV pop group The Monkees, has died at the age of 77.
"There are no words right now... heartbroken over the loss of my Monkee brother Peter Tork," bandmate Micky Dolenz tweeted.
Tork, who played keyboard and bass for the group, was diagnosed with a rare form of tongue cancer in 2009.
The Monkees were huge in the 1960s, with hits like I'm A Believer and Daydream Believer.
A post on Tork's official Facebook page said "the devastating news" was being shared "with beyond-heavy and broken hearts".
It said: "Our friend, mentor, teacher, and amazing soul, Peter Tork, has passed from this world."
A message posted on the band's official Twitter page said that Tork had "passed peacefully" and invited fans to share their favourite memories by adding their comments.