"The lights went out and Roman candles went off," and someone cursed, said Del Kinswoman, who attended the concert with her husband, Eddie, an advertising photographer for the Casper Star-Tribune.
They said Lee was taken to the hospital by ambulance.
Lee had been hoisted on a wire and was swinging back and forth between several drum sets perched several feet above the stage when the fireworks went off, said Tom Morton, a Star-Tribune reporter who was at the concert.
Band member Vince Neil told the audience they couldn't perform an encore because Lee was injured and needed medical attention, Morton said.
Wyoming Medical Center has not commented on Lee's injuries.
Motley Crue was scheduled to perform in Bismarck, N.D. on Friday and in Sioux Falls, S.D. on Saturday, according to the group's Web site.