Music lovers worldwide are mourning the loss of rock legend Malcolm Young.

The guitarist and co-founder of AC/DC died Saturday, the band announced on it’s website. He was 64.

Rolling Stone magazine reported that Young had been suffering from dementia.

PHOTO: Rhythm guitarist Malcolm Young from Australian rock band AC/DC poses for a portrait in London, Aug. 1, 1979.Fin Costello/Redferns/Getty Images, FILE
Rhythm guitarist Malcolm Young from Australian rock band AC/DC poses for a portrait in London, Aug. 1, 1979.

Shortly after the announcement, many rock musicians, including Ozzy Osbourne and Eddie Van Halen, took to social media to pay tribute to their colleague and friend who helped launch the Australian rock band in 1972.

Here are some who posted about Young:

It is a sad day in rock and roll. Malcolm Young was my friend and the heart and soul of AC/DC. I had some of the best times of my life with him on our 1984 European tour. He will be missed and my deepest condolences to his family, bandmates and friends.

— Eddie Van Halen (@eddievanhalen) November 18, 2017

So sad to learn of the passing of yet another friend, Malcolm Young. He will be sadly missed. God Bless @ACDCpic.twitter.com/HuEp3kCuyQ

— Ozzy Osbourne (@OzzyOsbourne) November 18, 2017

RIP Malcolm Young

Legend.

He was the founding member of AC/DC & the engine that roared behind the most powerful band in the world.

He wrote Back In Black, Highway to Hell, You Shook Me All Night Long, Highway to Hell, so many songs…

Travel safely to the stars, Malcolm.

Legend. pic.twitter.com/xfjylBbh4u

— Ryan Adams (@TheRyanAdams) November 18, 2017

RIP Malcolm Young ?? pic.twitter.com/7kHpkg6DK9

— Garbage (@garbage) November 18, 2017

“I’m sad to hear of the passing of Malcolm Young. It was great to get the opportunity to open for AC/DC on the Highway To Hell tour & we certainly learned a thing or two. He was an incredible guitar player & the glue for that band onstage & off. RIP Malcolm, say hi to Bon.” – Joe

— Def Leppard (@DefLeppard) November 18, 2017

Sad news about Malcolm Young. Dementia is such a horrible disease. pic.twitter.com/hpjrlffVLX

— Geezer Butler (@GZRMusic) November 18, 2017

Rest in rock power AC/DC’s #MalcolmYoung, #1 greatest rhythm guitarist in the entire history of rock n roll. THANKYOU for everything. pic.twitter.com/boXBDkJJ6W

— Tom Morello (@tmorello) November 18, 2017