Chino, Calif., police are investigating how and why an officer’s AR-15 accidently discharged , injuring three students, during Red Ribbon Week activities Wednesday morning at Newman Elementary School, the Inland Valley Daily Bulletin reports .

The rifle was mounted to a police motorcycle that was on display during the activities, said Tamrin Olden, Chino police spokeswoman.

“The event and activities did not involve the display or use or demonstration of any weapons,” Olden said during a press conference Wednesday evening.

During the morning activity, a child was able to approach the motorcycle and pull the trigger of the rifle that was locked in to a weapons mount on the side of the vehicle, police said.

Olden said it is likely metal debris struck two children resulting an extremely minor injuries. They were transported to a local hospital for treatment. One other injured student was treated at the school.