The band, part of Norway’s death metal music scene, was carving up a dead sheep as part of its stage act when the animal’s head flew off lead singer Maniac’s knife and struck Per Kristian Hagen, 25.

The show was Thursday in Bergen, 487 kilometers (302 miles) west of the capital, Oslo.

“My relationship to sheep is a bit ambivalent now. I like them, but not when they come flying through the air,” Hagen told The Associated Press Monday from his hospital room. “I have a headache now.” He is expected to recover.

Hagen, a Mayhem fan, filed involuntary assault and battery charges against the band. The charges carry a maximum sentence of six months in prison.

Mayhem member Rune Eriksen, whose stage name is Blasphemer, said the incident was unfortunate.

“The whole thing was an accident, but maybe it would be an idea for another show,” he said.

Eriksen promised Hagen a free ticket to the group’s next performance.

Police detective Carl-Petter Leganger told the AP an investigation has started, but “nothing suggests this was a conscious act.”