KNOXVILLE, Tenn. (WATE) — A high school teacher in Tennessee is reflecting on the semester she taught Ryan Knauss, a staff sergeant with the U.S. Army who was killed this week in an attack outside Kabul’s airport in Afghanistan.

Staff Sergeant Ryan Knauss, killed at age 23, was just 14 when he was in Angela Hoffman’s class at Gibbs High School. She taught Knauss for one semester in 2012, which was also her first semester as a teacher and Knauss’ first semester in high school.

“He had a very quiet but confident demeanor,” Hoffman said.

One of the first assignments Knauss completed in Hoffman’s class — an essay explaining who he was — would end up leaving a lasting memory with the teacher. It also gave a strong glimpse of his character, she said.

From his essay, Hoffman says she learned that Knauss was born and raised in Corryton, Tennessee, and liked to read. He also had dreams of joining the military. But Knauss, unknowingly, went on to describe the traits that he would ultimately exhibit after joining the service.

“In his essay, he wrote … that for him a role model is anyone who stands up against power to help others,” Hoffman said.

When she saw the news of Knauss’ death on Friday, Hoffman says she recognized the name from nine years ago. She immediately started digging through her classroom mementos from over the years and found a handwritten note of hers about the essay.

“He wrote that nine years ago as a 14-year-old boy, not knowing the man he was going to become. And that was just so powerful to find this in my handwritten notes,” Hoffman said.

Knauss, indeed, died being his own definition of a role model. He was one of 13 other servicemen killed in coordinated attacks outside the Kabul airport in Afghanistan on August 26.

He was 23 years old, and leaves behind a wife.