ANOKA — Anoka County authorities have charged a man who they say used a samurai sword to attack teenagers who were throwing toilet paper on his property.

Twenty-four year-old Nicholas Curtis was charged Wednesday with first-degree assault causing great bodily harm and second-degree assault. He could face up to 20 years in prison if convicted.

Police said the teens were throwing toilet paper in trees as a prank when Curtis came out with the sword early Tuesday. They said he smashed and stabbed through a car window, injuring a 17-year-old Coon Rapids boy.

The teen underwent surgery on his chest and abdomen. His condition wasn’t immediately available early today.

Curtis told police he saw the teenagers by his home and “felt threatened.”

Online jail records didn’t indicate an attorney or bond.