He was 47 years old.
Corey was a contributor to several metal blogs, and founded the Housecore Horror Film Festival with Phil Anselmo of Down.
Mitchell died the morning after the festival in Austin wrapped up.
The Austin Chronicle claims Mitchell was loading up his car with the help of a fan when he fell to his knees.
After Corey fell all the way down, the fan got him on his side and he called for help.
“We’re really just still in shock,” Anselmo told the Chronicle.
“After Danzig was done, Corey and I got up on stage and thanked all the bands and all the fans, the filmmakers, and the ‘Texas Chainsaw’ people. It’s all just horrifically surreal. This one hurts, man. They all do, but this has a special kind of hurt to it. The event was such a blast, such a success, and everybody had such a great time.
“Nobody worked as hard as Corey. He believed in it so fucking much. He fought for it every inch of the way. It’s like lightning striking, man; you just never know.”
At the time of his death, Mitchell — who wrote several books — was working on Anselmo’s autobiography “Mouth For War: Pantera And Beyond,” which is still due out next year through Simon & Schuster.
He is survived by his wife Audra and daughters Emma and Sabrina.