CADET, Mo. – The Kingston K-14 School District high school and junior high school are closed Monday after a student died by suicide, according to the district.

“This letter is to inform you of a sad tragedy that occurred at the senior high school this morning. Sadly a student took their life this morning,” the school district said in a letter to parents Monday morning.

The Washington County Sheriff is investigating why a Kingston High School student shot and killed himself in a school bathroom Monday.

Luke Cook, 17, ate breakfast with his friends like normal, then apologized for something he was about to do, Sheriff Zach Jacobsen said.

Those friends didn’t even have the chance to report their concerns before another student found Cook lying on the ground in the bathroom and called for help. Administrators found the gun. Cook died before he could be taken to the hospital, Jacobsen said.

The sheriff is working with the FBI and ATF to track where Cook got the weapon.

"We have many kids who are hurting and staff members who are in shock today,” Superintendent Alex McCaul said.

The 400 middle and high school students were sent home at 9 a.m. Counselors will be available for students and staff Tuesday morning when students returned to classes.

“Talk. I think that's the key. There's still a stigma about mental health, that if you have a mental health issue there's something wrong with you. Many people have needs. They need to talk about something. So, if you know somebody who's suffering, talk to them,” McCaul said.

McCaul said the district will also take a closer look at security because the student was able to bring a gun into the school without anyone noticing.

"We don't search each student as they come in,” he said.

The high school is a secure building. Strangers have to get buzzed in to get access to the hallways, and McCaul said he doesn’t want to make a school environment feel like a prison.

"We will obviously discuss this at our next school board meeting. We were already planning on discussing it after the tragedy in Florida. What more can we do?"

If you or someone you know needs help with suicide, click here for information and resources from the National Suicide Prevention Lifeline.