OAKLAND -- A 13-year-old was in juvenile custody Wednesday after a handgun hidden in his backpack went off as he sat with other students in a classroom, school officials said. Fortunately, authorities said, no students were injured in the incident.

Oakland school district spokeswoman Laura Moran told KTVU that a class was underway at Cole Middle School on Tuesday when a loud bang interrupted the teacher.

“There were three students sitting near the wall, near the radiator, and initially there was a loud bang,” Moran told KTVU. “The teacher thought there was an explosion with the radiator so he had the students leave the room…The teacher did an outstanding job managing the situation.”

School officials immediately sent in a security team and evacuated the students to the gym.

“We then had our own police services come down and conduct a search,” she said. “They found a loaded handgun… and talked with the students.”

School officials said the single shot hit a radiator and ricocheted.

After the questioning, the 13-year-old boy was taken into custody.

School officials also wrote a letter explaining the incident to parents and it was sent home with the students at the end of day. However, some parents complained to KTVU about the delay in notification.

“We are reviewing how we managed the situation,” Moran said.