The department said Maj. Donald Lamar accidentally fired his gun while placing it in his holster during a weapons safety class for deputies, the New Bedford (Mass.) Standard-Times reported Wednesday. No one was injured.

Sheriff Thomas Hodgson said Lamar, who has been a certified firearms instructor since 2005, displayed a "gross error in judgment" when he failed to verify that his weapon was empty.

"He didn't clear his weapon before he went in the classroom, which is something he did every day," Hodgson said. "In fact, he would often show students while in class that his weapon was clear."

Lamar has been transferred to the sheriff's traffic division pending the outcome of an investigation into the incident.