The 19-year-old U.S. Air Force Academy cadet who was found unresponsive in her dorm room in early September died from a rare bacterial infection "associated with a toxic shock-like syndrome," a coroner has announced. 

Avery Koonce had been fighting a cough before dying on Sept. 4 in Colorado from "Paeniclostridium sordellii sepsis complicating parainfluenza laryngotracheobronchitis," according to an El Paso County Coroner’s Office report obtained by Fox21 News. 

Coroner Leon Kelly wrote in the report that Koonce had an abnormal fluid build-up in her left lung along with the bacterium Paeniclostridium sordellii, which can cause "serious disease or death in various clinical settings including airway infection and sepsis," according to the Colorado Springs Independent. 

The bacteria "has been associated with a toxic shock-like syndrome that can rapidly progress to death," and "It's likely that the bacterial infection was secondary to the parainfluenza infection… that resulted in… symptoms of severe cough and upper airway inflammation and edema," the newspaper cited the report as saying. 

US AIR FORCE ACADEMY CADET, 19, IS FOUND DEAD IN HER DORM ROOM 

Air Force Cadet Avery Koonce

Avery Koonce was found dead in her dorm room on Wednesday, the U.S. Air Force Academy says. (U.S. Air Force Academy)

The Centers for Disease Control and Prevention describes sepsis as "the body's extreme response to an infection" that happens "when an infection you already have triggers a chain reaction throughout your body." 

The U.S. Air Force Academy said Koonce, a 19-year-old from Taylor, Texas, was set to graduate in 2028 and was a member of the women’s track and field team. 

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US Air Force Academy

A fighter jet is seen on the grounds of the United States Air Force Academy near Colorado Springs, Colo. (Education Images/Universal Images Group via Getty Images)

"We lost an incredible teammate... While only with us for a short time, Avery positively impacted her unit, her intercollegiate team, and her class – her loss will be felt across USAFA," Academy Superintendent Lt Gen Tony Bauernfeind said at the time of Koonce’s death. "Our team is focused on providing support to Avery’s family, Cadet Squadron 38, the Track and Field team, and the entire Academy family."

Koonce attended Thrall High School, according to the Austin American-Statesman, which quoted the district’s superintendent as saying that she was the president of the student council and leader of the National Honor Society.  

U.S. Air Force Academy gun demonstration

Tusajigwe Owens demonstrates how to operate an air gun before cadets participate in a training exercise at the U.S. Air Force Academy in September 2023. (Reuters)

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U.S. Rep. Pete Sessions, who nominated Koonce to attend the U.S. Air Force Academy outside of Colorado Springs, also told the Austin American-Statesman that he was "incredibly saddened to hear about the loss of Cadet Koonce."