Rob Zombie was forced to cut short his July 20 set at the Rock Fest in Cadott, Wis., due to throat problems. After performing only two songs, a raspy-voiced Rob Zombie apologized to the festival crowd before walking offstage to a chorus of disappointed groans.

Rob Zombie was the closing headliner of the four-day festival, which featured Sammy Hagar, Five Finger Death Punch and Aerosmith as top billers for the previous three days.

"I've never done this before," Zombie said to the crowd after finishing 'Superbeast.' "I can't even talk, man. There's no way I can do this show, I'm sorry. It's f---ing bulls--t, I know. We don't want to give you a s--t show, I'm sorry. What can we do?"

Rock Fest shared a statement from Rob Zombie apologizing once again earlier today:

Sorry, everybody. I wish my voice wasn't so f---ed. I knew from the first second we started that it was impossible to get through the show.

The festival organizers also offered an apology for Rob Zombie's early exit:

Sorry Rock Festers. We didn't mean for Rock Fest to end this way. What we were told is Rob Zombie's voice went. We tried to get him back on stage, but to no avail. That's what took so long. Thanks for being the most amazing rock fans around. Travel safely.

Rob Zombie will kick off a new tour in Portland, Ore., on Sept. 8. For Zombie's full list of dates, click here.

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