Staffers quickly locked down the school and evacuated about 700 eighth and ninth graders, along with students from an adjacent elementary school, to a safe location, police Capt. Randy Dickerson said. The eighth grader was found dead in a hallway, Dickerson said.
Some students who fled the building said they found out it was a suicide from news reports. Other students who had witnessed the shooting spread word that a classmate had killed himself, police said.
Jake Green, 14, said he was among dozens of students who meet to pray every morning who heard the single shot ring out from an adjacent hallway about 10 feet away.
"We heard this loud boom and everyone just got quiet," Green said. "No one said a word."
A teacher yelled at the students to get out of the building and head to a playground at the elementary school, Green said.
"Everyone was really scared. We didn't know if the kid shot himself or if there was a shooter outside the school who shot in," Green said. "Everyone didn't know what was going on, so they were screaming and running as fast as they could to get to the playground."
Police didn't say what prompted the shooting but said no other students were at risk.
"It doesn't appear that anyone else was in danger or threatened," Dickerson said.
Dickerson said the eighth grader shot himself once in the head with a handgun. Police wouldn't say where the weapon came from or how he got it into the school.
Superintendent Ann Caine said there aren't any metal detectors at the school. She expects that there will be discussions about the policy, but said Wednesday that school officials were still trying to deal with the shooting.
The teen had been a good student who got along with other kids, and there was no indication he was bullied, Caine said.
Green said that students who were already in their classrooms when the shooting happened were locked inside the building for about an hour after that.
"It was really scary," said Green, a ninth grader. "Everyone's kind of traumatized and doesn't know how to act or respond."
Counselors will be available for students, Caine said.
Kenny Monday told The Associated Press that his son, Kennedy, heard the gunshot but did not witness the shooting.
"It's so sad that the kid lost his life, but we're just glad he didn't shoot anyone else," Monday said.
Stillwater Junior High sent a statement to parents saying there had been a "single shooting incident" at the school and that staff and students had been moved to a safe location. Parents were told to pick up their children at a nearby shopping center. Stillwater is located about 70 miles west of Tulsa.
"It is with a heavy heart that I inform you of a tragic incident at our (school) this morning," Caine said in a letter to parents. "At 7:50 a.m. one of our students died as a result of a self-inflicted gunshot wound. All other students and staff are safe."
Caine told reporters that the family of the student had been notified.
"This is a family who is grieving right now," Caine said.
Associated Press writers Ken Miller and Sean Murphy in Oklahoma City, Ashley M. Heher in Chicago and Jeannie Nuss and Jill Bleed in Little Rock, Ark., contributed to this story.