Armed police evacuated a school after a student wearing a Darth Vader costume was mistaken for a potential attacker in a bullet-proof vest.
Officers arrived at Ashwaubenon High School in Green Bay, Wisconsin, after a parent called to say they had seen someone walking through a back door carrying a bag and wearing what looked like body armour and a mask.
Students were evacuated and another nearby school was placed on lockdown as armed officers searched the area.
But the alert ended when officers realised the suspected assailant was a child who had dressed up for Star Wars Day – an annual celebration observed by fans of the sci-fi franchise.
Police captain Jody Crocker said the parent was right to call the emergency services.
He said: "The saying ‘If you see something, say something’ certainly applies to this and we always encourage people to report suspicious activity.
"The outfit actually looked like he wearing a bullet-proof vest or a flak jacket.
"Coupled with wearing that mask and walking into the back door of the school (it) made a person very concerned."
He added that the student would not be punished "as it has been determined that this was merely a mistake or lapse in judgement".
School headteacher Brian Nelson said he would speak to students about the incident as costumes "are not part of the dress code".
He said: "We’ll move forward from this and make it a learning experience for our students so we don’t have to repeat this."
(c) Sky News 2017: Student in Darth Vader costume sparks armed police alert at US school