The parents of Tyler Hilinski announced Tuesday during an interview on NBC’s TODAY show that their son had the degenerative brain condition chronic traumatic encephalopathy (CTE) when he died from a self-inflicted gunshot wound to the head in January.

The Mayo Clinic in Florida contacted Mark and Kym Hilinski after Tyler’s death and the family agreed to give the hospital his brain and perform an autopsy that came back with positive results for Stage 1 CTE.

“The medical examiner said he had the brain of 65-year-old, which is really hard to take,” Mark said during the interview. “He was the sweetest, most outgoing, giving kid. That was difficult to see.”

CTE is a brain disease that can only be discovered post-mortem and is commonly found in athletes who have suffered repeated hits to the head and symptoms of the disease include depression, short-term memory loss, emotional instability and suicidal thoughts, according to the Mayo Clinic.

The VA Boston Healthcare System and Boston University School of Medicine conducted a study of the brains of 202 deceased American football players last year that showed 87 percent of the players had CTE. Only one of the 111 brains of deceased NFL players studied didn’t have CTE.

Hilinski’s parents spoke on TODAY to discuss a new Sports Illustrated documentary that shows how they have dealt with his suicide and raised awareness for mental health issues through the Hilinski’s Hope Foundation.

In the documentary, Kym reflected on how playing football could have played a role in Hilinski’s suicide.

“Did football kill Tyler?” Kym said in the documentary. “I don’t think so. Did he get CTE from football? Probably. Was that the only thing that attributed to his death? I don’t know.”

In the interview, Kym said there were no signs that indicated Hilinski was struggling with mental health issues.

“There weren’t really any verbal signs from Tyler to us or anybody at Washington State that he was suffering,” Kym said.

Although, Hilinski’s parents admitted they noticed a change in their son after WSU lost 58-37 to University of Arizona on Oct. 28, including him being less responsive to calls and texts the rest of the season.

“The reality is that we missed it, and we let him down,” Mark said in the documentary.

If you are in need of emotional support, call the 24-hour a day National Suicide Prevention Lifeline at 1-800-273-8255, which is a confidential service to those in distress.

WSU Counseling and Psychological Services can also be contacted online, and after hours at 509-335-2159.