Journey co-founder George Tickner has died at the age of 76, his former band mate Neal Schon announced on social media.
No cause of death has been disclosed to the public yet.
Schon posted a video of himself playing guitar at home alone on Instagram Thursday.
"Some smooth Strat to EZzzzzzz your soul. Prayers for George," Schon captioned the clip.
Tickner co-founded the rock band alongside Schon, Prairie Prince, Gregg Rolie and Ross Valory. He was Journey's original rhythm guitarist.
The musician also helped write "Of a Lifetime," "Topaz," "Mystery Mountain," "You're on Your Own" and "I'm Gonna Leave You" -- songs on the group's first three albums -- Journey, Look Into the Future and Next.
He quit the band to pursue a career in medicine, but reunited with the contemporary lineup of Journey, including Schon, when the group was presented with a star on the Hollywood Walk of Fame in 2005.
"Rest peacefully, Dr. George Tickner.. you will be missed immensely!" Schon wrote separately on Facebook.
"Thank you for your incomparable contributions to Journey's early years. The reason he left was to attend Stanford University on full Scholarship, earning his PhD. Fly free above the stars, Sir."