It's a reality schools across the country face. An armed intruder open firing on student in school. Oklahoma's largest school district does not take the threat lightly and has stepped up efforts to combat the all-too-real threat.
Sgt. Matthew Sites with the Oklahoma City Police Department is one of the district's school resource officers. He's been on the job eight years and describes himself as the school's last defense. Armed with a gun and handcuffs, he has to be ready to react at any moment to any situation.
"As a police officer, I'm the last line of defense for these guys," said Sites. "My first year here we had over 150 arrests, which is just unheard of for a school setting."
These hallways have known gang-members and Sites says the reality of a school shooter is always in the back of his mind. From these more serious threats to students fighting on campus, Sites is constantly training for the "what if" of his job, including an active shooter, even if he thinks chances of that happening are slim.
So Sites focuses on what goes on throughout the school every day. Staying aware of anything out of the ordinary.
"It is a pulse. I can tell when my kids are going. We have fights just like any school does and I can tell when there's a fight brewing or when something is going to go down just by the feel of the kids."
But Sites is a one-man-team. To get that pulse he tries connecting with as many of the 1,400 students as often as he can.
"They have to understand that I'm not there just to arrest you. I'm not there just to arrest your parents or deport people," he said. "That gap is that hardest part."
During News 9's visit to Capitol Hill High, a father came in asking Sites for help with his son. He explained the 16-year-old was getting involved with gangs and thought his family might be in danger. Sites did not hesitate, offering up several options to set the students straight.
That has been one the keys to the success at Capitol Hill High. Building trust with parents and surrounding neighborhoods with the hope of changing a culture of suspicion built up between the neighborhood and police for decades.
The strategy is working at Capitol Hill High School. Since Sites has taken over as the school's resource officer, annual arrests have fallen to only about a dozen.
Each of Oklahoma City's high schools have an armed school resource officer on campus.