A man dressed as Santa Claus was knocked unconscious by a thrown object that hit his face while he was riding on the back of a truck decorated as a sleigh.

Kevin Smith says he never saw what hit him Saturday. Whatever it was, it broke his nose and gave him a concussion and two black eyes.

"One second I was up there waving to people, and the next minute I wasn't," Smith said.

He was taking part in Santa Run, sponsored by the firefighters union, which features off-duty firefighters who dress up as Santa and ride through residential areas handing out candy to children.

Other volunteers realized something was wrong after they hadn't heard from Smith for a few minutes. They stopped the truck and found him lying unconscious.

"It pretty much cold-cocked him," fire Lt. Scott Himelspach said.

Smith awoke in the back of the sleigh.

"They thought I'd spilled my hot chocolate, but then they realized it was blood," Smith said. "The rest of the night was kind of hazy."

Smith, a firefighter for eight years, said he hoped to return to work on Christmas Day.

Assistant Fire Chief Brian Schaeffer said an assault report was filed with police but that no witnesses have come forward.