CHINO, Calif. – Three students at a California elementary school were injured Wednesday after a student discharged an assault rifle mounted on a police motorcycle that was on display, an official said.

The AR-15 assault rifle was mounted on the motorcycle that was on display during a drug prevention event, said Tamrin Olden, a spokeswoman for the Chino Police Department.

“The rifle was secured in the mount on the motorcycle during the incident,” Olden said at an evening news conference. “The child did approach the mounted rifle.”

The students suffered minor injuries, Olden said. None was hit by gunfire. Two were likely struck by metal debris, resulting in “extremely minor injuries,” she said.

She described the weapon as an AR-15 that was locked onto the bike. Police were investigating how the weapon discharged, and Olden said “there are several fail-safes in place” to prevent a discharge.

Law enforcement officials were at Newman Elementary School in Chino for activities related to the nationwide drug-prevention campaign when the weapon was discharged during a demonstration.