HOUSTON - A 13-year-old high school student in the US state of Oklahoma killed himself Wednesday with a gunshot to the head, US media reported.

The eighth-grader at a junior high school in the Oklahoma city of Stillwater, identified as Cade Poulos, shot himself in a hallway Wednesday morning before classes, the news website NewsOn6.com quoted police as reporting.

"It is with a heavy heart that I offer condolences to this student's family," Superintendent of Stillwater Public Schools Ann Caine said. "We're never ready for a day like this."

The boy killed himself inside a hallway near classrooms and lockers, Randy Dickerson of Stillwater Police was quoted as saying.

Several students and faculty were preparing for classes and were witness to the shooting, Dickerson said.

Some schools in the area were under a temporary lockdown after the shooting.

A Facebook page set up in Poulos' honor Wednesday morning had many posts suggesting the boy was picked on frequently and students who gathered outside the school told NewsOn6 that he was a victim of bullying.

Dickerson said he was unable to confirm whether the student had been bullied as an investigation had just begun.