Nick Menza, former drummer for Megadeth, passed away yesterday after collapsing while performing onstage with his band Ohm in Los Angeles. He was 51.

While the cause of death is not official, as Consequence of Sound reports, a statement released by the band’s management says that early indications point to a massive heart attack suffered by Menza while onstage.

Menza was with Megadeth from 1989 to 1998 and performed on some of their most popular albums, including Rust in Peace, Countdown to Extinction and Youthanasia.

Megadeth founder and frontman Dave Mustaine expressed his sorrow via Twitter this morning, writing “TELL ME THIS ISN’T TRUE! I woke at 4 AM to hear Nick Menza passed away on 5/21 playing his drums w/Ohm at the Baked Potato. #nickmenzarip.” Former guitarist for the band Marty Friedman took to Facebook to honor his former bandmate, writing “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.”