TV and sci-fi fans are mourning the loss of actor Ron Glass, who died on Friday, November 25 of respiratory failure at the age of 71. Glass was known for his role on the long-running workplace sitcom Barney Miller, as well as portraying the character of Shepherd Book on the sci-fi series Firefly and its film follow-up Serenity.

Glass’ television career spanned several other well-known series, including All in the Family, Sanford and Son and Friends. He also lent his voice to shows like Rugrats and video games such as Fable II. Recently, he had appeared in episodes of Agents of S.H.I.E.L.D. and CSI.

Many of Glass’ former Firefly castmates took to social media over the weekend to share fond memories of their late co-star–including Nathan Fillion, Jewel Staite, Alan Tudyk, Adam Baldwin and Sean Maher–as well as the show’s creator Joss Whedon:

He got there with grace, humor & enormous heart. He was, among so many other things, my Shepherd. Raise, appropriately, a glass. Rest, Ron. pic.twitter.com/yzPly7TmgE — Joss Whedon (@joss) November 26, 2016

"Shepard, don't move." "Won't go far." We love you, Ron Glass. Don't go far. A photo posted by Nathan Fillion (@natefillion) on Nov 26, 2016 at 2:09pm PST

Happy rebirth, dear Ron Glass. Among the kindest and gentlest souls to have walked this earth with us.https://t.co/rF1bDPxeRa — Adam Baldwin (@AdamBaldwin) November 26, 2016

Ron Glass was one of the greatest actors to work with. His laugh was beyond infectious and his generosity was ever present. #ripronglass — alan tudyk (@AlanTudyk) November 26, 2016

Ron Glass. What an honor it was to know you, to work beside you and to have called you my friend. You will be missed. I love you sir. — Sean Maher (@Sean_M_Maher) November 26, 2016

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