(CNN) There was a gunman in the school. Owen, an eighth-grader at STEM School Highlands Ranch , texted his mother.

The messages threw her into a panic.

"I was terrified of this happening," Cami Brainard, 34, told CNN Wednesday. "I thought about it every day."

"And it happened."

They exchanged texts for about 14 minutes as Owen hid in a classroom. Brainard asked that her son only be identified by his first name.

One student was killed and eight others were injured Tuesday in the shooting at the suburban Denver school, not far from Columbine High

Brainard shared the text messages she exchanged with Owen on Facebook, along with a brief recording Owen made on his phone during the shooting.

"It's a school shooting"

Brainard was at the hair salon where she works when the messages started flashing on her screen.

"There were gunshots. We are about to get escorted to leave," her 14-year-old son wrote around 2:09 p.m., minutes after the shooting started.

"Where?" she replied. "Can you call me."

"No," he wrote. "We have to stay quiet."

The sight of police cars and fire engines, their sirens wailing, zooming past the salon several miles from the school soon confirmed her fears, she said.

"Owen are you ok?," she wrote.

"Sort of," he responded.

Brainard's family had been touched by a mass shooting before. Her sister-in-law was at the Route 91 Harvest music festival in October 2017 when a gunman killed 58 people; she survived.

Not again, Brainard thought.

"Please tell me what's going [on]," she wrote.

"It's a school shooting," Owen wrote.

Brainard said she was becoming hysterical. "I just kept repeating myself," she recalled.

"Please keep texting me," Brainard wrote. "What's going on."

"We can't we have to keep our hands free," he wrote.

At 2:23 p.m., he texted: "We are outside."

Lockdown, gunshots and yelling

Later that night, Owen played his mom the recording he made when his cell phone was in his pocket.

"Attention, please. Lockdown. Locks. Lights. Out of Sight," played repeatedly in the background.

"They found him," Owen whispered on the recording.

Then, gunshots and yelling in the background.

"Knowing that that's my child and that he actually had lived through that ... he's going to be scarred for the rest of his life," Brainard said

Owen said his "legs were shaking and his teeth were chattering he was in such fear," Brainard wrote on Facebook.

Cami Brainard

Brainard said she debated whether to post the audio.

"I don't want to be responsible for added trauma," she wrote.

But she said she decided to post it "before people don't pay attention anymore, before people don't care about it anymore."

"I think the more people are forced to see these things, the more exposure that there is for these things, the more people realize that it can happen to them," she said.

"It's going to happen again, unless we do something," she said.