A criminal justice instructor at Technology Center of DuPage in Addison accidentally discharged a handgun during class Friday afternoon, striking a file cabinet and hollow wall, officials said.
The instructor, a retired FBI agent, wasn't authorized to have the gun on school property, said Jim Thorne, the school's director.
"It's not part of the curriculum. It's nothing we knew he had," Thorne said.
Three students were watching the instructor's demonstration about 1:30 p.m. in an office adjacent to a classroom, where other students were preparing for the start of class, Thorne said.
No one was struck by the bullet, which ended up lodged in another classroom, he said.
After the shooting, a school administrator came to the classroom and escorted the instructor from the building. He was sent home and has been placed on administrative leave until further notice.
Whether the instructor faces termination or disciplinary action won't be determined until after an investigation into the incident is complete, Thorne said.
Addison Police Department Director Tim Hayden said the instructor has been questioned by police, but it's too early to say whether he will face any criminal charges.
Thorne declined to identify the teacher by name, but a directory on the school website lists only two criminal justice instructors -- one of whom is a former FBI agent.
That teacher, James Whitmer, declined to discuss the shooting incident when reached by phone.
The school offers career and technical education classes to DuPage County high school juniors and seniors as part of their regular high school curriculum.
A school news release said officials contacted the parents of the students who were in the class to "express our sincere apology that their children's safety was put at risk today."