A teenager was arrested for trespassing after he went to his old high school and shot an art teacher with a toy gun last week, Nassau police said.

Nineteen-year-old Kurt Kiernan of Seaford walked into an art class at Seaford High School and shot the teacher with what was described as a “Nerf dart gun” on the morning of Oct. 14, according to 7th Squad detectives. The principal then called police.

Kiernan was “found wandering the halls” and charged with criminal trespass.