Friday began as a routine day for 15-year-old Isabelle Laymance and her mom, Deedra Van Ness.

Deedra dropped her daughter off at Santa Fe High School, told her she loved her and headed home to get ready for work.

Half an hour later, their lives were forever changed.

Isabelle was in her first period art class when she heard gunshots.

“First he said ‘Surprise, m------ f------,’ and then he started shooting and that’s when he shot a kid,” Isabelle told the Washington Post. “And then people were running out of the classroom and he was chasing after them, trying to kill them.”

They tried to go through a back door but it was locked and they were trapped.

Deedra heard her phone ring, saw it was Isabelle calling and figured she had forgotten something.

“As I answer the phone, she is whispering and I can barely understand her. Then I hear her whisper… mom, they are shooting up the school, I'm hiding in a closet. I love you mom,” Deedra posted on Facebook. “In the background, I hear gunfire. I beg her to stay on the phone and she says other kids with her want to call their parents and don't have phones. I beg her not to hang up as the call drops. I was frozen, standing there with no idea what to do next.”

Photos: The victims of Santa Fe High School shooting

Isabelle hid in that closet with seven terrified classmates. She told her mother the gunman fired several shots into the closet, killing two of the students.

When he left, they could hear him going from one art classroom to another.

VIDEO: Community gathers for moment of silence

“He went to the other room and he was looking at the bodies, and he went ‘Woo hoo’ and stuff like that, like cheering himself on," she told the Post.

Photos: Memorial grows at Santa Fe High School

He came back to their room and heard a cell phone ringing. Isabelle said he began to taunt the students he knew were barricaded in the closet.

“Whose phone is that? Do you want to pick it up?” he shouted.

“I send a group text to my family telling them she’s hiding and to NOT to call Isabelle and give away her hiding place,” Deedra said. “We make our way towards the school and are passed by no less than 30 emergency vehicles along the way. During this time, we are frantic and both of our phones are blowing up. All we can do is stare at them praying she calls us again.”

Isabelle called 911 and the dispatcher told her officers were in the building. Stay on the line. Be quiet. Don’t move.

The students could hear the suspect talking with officers. And reloading his gun.

“The shooter kept on asking if they were going to kill him or shoot him when he gets out,” Isabelle said.

She said 5 or 10 minutes passed, before they heard him open the door and the officers yelled, ‘Put your hands up, get down on the ground!’”

The gunman told officers he had planned to kill himself, according to court documents, but lost his nerve and surrendered.

"As they are leaving the closet, they are walking past bodies in the classroom and hallways," according to Deedra. "They are frisked and removed from the building where they are placed in police cars awaiting questioning."

Deedra and her Kenny had rushed to the school but they weren’t allowed to see Isabelle.

Hours would pass before they were finally reunited.

“Finally, I get to hold my baby as we both cry and I try not to notice the blood on her.”

When they got home, they learned their son’s best friend was killed in the shooting.

By Friday night, 10 families would learn their loved ones – eight students and two teachers -- didn’t survive.

Those who did are left to grieve as they struggle to cope with what happened during that 30 minutes of terror.