Fans ran for cover when a lightning bolt hit came down at the outdoor Country Thunder music festival in Wisconsin.
The Kenosha County Sheriff's Office says a 22-year-old woman may have been struck after she was found face down, and bleeding from her ear.
"Her phone was completely shattered and she was just laying on her stomach, completely unresponsive, but she did have a pulse," said witness Kayla Byrne.
The woman was rushed to the hospital in an unknown condition.