As the music world continues to mourn, the cause of death for drummer A.J. Pero has been revealed. Pero's Twisted Sister bandmate Dee Snider revealed what happened when questioned by a fan on Twitter.

The vocalist stated that Pero died of a massive heart attack. He added that the drummer had advanced heart disease. Snider has been quite active online since the death of Pero on March 20. He also revealed that he's been having difficulty coming to terms with the fact that his longtime friend is gone.

Since Pero's death, the rocker and many of the band's fans have visited Snider's twitter account to pay their respects with videos, tributes and memories. Snider himself stated, "Thank you all for the outpouring of love and respect for Twisted Sister drummer A.J. Pero. I wish he was here to see it. RIP my brother."

Pero also played with Adrenaline Mob, who have also paid respect to the drummer's memory. Former Adrenaline Mob drummer Mike Portnoy and ex-Breaking Benjamin drummer Chad Szeliga joined the band onstage for their first show following Pero's death. Szeliga has agreed to sit in for Adrenaline Mob while they complete their current touring plans. Meanwhile, Twisted Sister's Jay Jay French joined Adrenaline Mob onstage for their encore of Twisted Sister's 'You Can't Stop Rock 'n' Roll." To see footage of the performance, click here.

Rockers We Lost in 2014