Nick Menza, a former drummer for the metal band Megadeth, has died after he collapsed on stage during a show in California. He was only 51 years old.

According to The Guardian, Nick Menza collapsed right before OHM played their third song in the set. Mike Simpson, a fan who was in the audience share that “I was watching his band OHM at the Baked Potato tonight and he collapsed on stage. Paramedics were saying it looked like a heart attack,” he wrote on Facebook.

The unimaginable happened, and Nick Menza passed away right before the eyes of the audience. The news shocked many in the music industry, including Megadeth’s frontman Dave Mustaine, who tweeted that he was “gutted” upon hearing it. “Tell me this isn’t true,” he wrote on Twitter.

Megadeth guitarist Marty Friedman paid him a lovely tribute on Facebook saying, “We all know the great and unique drummer that Nick Menza was, but he was also a trustworthy friend, a hilarious bandmate, as well as a very loving dad. I’m beyond sad, did not see this coming at all. RIP Brother.”

J Marshall Craig, Menza’s biographer, asked for prayers from the public for the family that Menza have left behind. “We ask for prayers for Nick’s family, his family, and especially his two sons and their mother, Teri,” Craig said.

“He just spend nearly two weeks with the boys in the Pacific north-west and was absolutely glowing. He was scheduled to fly to my home in Cape Cod tomorrow so that we could finish the comic-book version of the book we wrote on his life, MenzaLife, both of which were slated for release late next month. This morning we are all too numb to think about anything but Nick’s family.”

Megadeth paid tribute to its fallen former member on its website Sunday. “In Remembrance of Nick Menza,” the page says.

Nick Menza left Megadeth in 1997 when he had to have knee surgery and could no longer tour. Nick founded OHM along with another Megadeth album, guitarist Chris Poland, in 2002. The band played regularly at the Baked Potato club.

Ultimate Classic Rock reports that hours after the sad news broke, Megadeth tried to make an effort to do something for the family of Nick Menza. Mustaine shared that he’s ready to perform a benefit concert and hoped that other former members will also be a part of the event.