Polish rock band Riverside took to social media yesterday (Feb. 21) to announce the tragic passing of guitarist Piotr Grudziński. The musician (pictured far left above) passed away at the young age of 40.

Formed in 2001, Riverside has become a popular rock band in Poland, releasing six albums of etherial and gripping music. Grudziński performed on all six records, the most recent being Love, Fear and the Time Machine in 2015. Riverside had been teasing new material up to just a few days before Grudziński suddenly passed away. The cause of Piotr Grudziński’s death has not been revealed.

Riverside posted about Grudziński’s death via Facebook:

In our deepest pain and disbelief we would like to inform you that our dearest friend and brother Piotr Grudzinski has passed away this morning. We kindly ask you to respect the privacy of his family and friends.

Drumming legend Mike Portnoy tweeted about Grudziński’s passing. Apparently, the guitarist had watched The Winery Dogs perform in Warsaw on Feb. 20:

Progressive metal act Haken also memorialized Grudziński:

We’d like to send our deepest condolences to the loved ones of Piotr Grudziński. In his memory, listen to Riverside’s music in the player below.

Riverside, 'Discard Your Fear'

Rockers We've Lost in 2016