DALLAS — Researchers at the Boston University CTE Center announced on July 8, 2026, that former Dallas Cowboys defensive end Marshawn Kneeland was diagnosed with stage 1 chronic traumatic encephalopathy (CTE). Kneeland died by suicide from a self-inflicted gunshot wound on November 6, 2025.

Kneeland was 24 years old at the time of his death. He was selected by the team in the second round of the 2024 NFL Draft. His death followed a police pursuit in the Dallas metroplex that began after a traffic violation.

During the pursuit, police officers received information that Kneeland had expressed suicidal ideations. The NFL was also notified that he was texting goodbye messages to family members prior to his death. Catalina Mancera, Kneeland's girlfriend, gave birth to their son, Makhai, on June 11, 2026.

Ann McKee, Director of the Boston University CTE Center, stated, "Unfortunately, I was not surprised to find CTE in the brain of Mr. Kneeland, because we have found this progressive brain disease in nearly half of the athletes we've studied who have died before the age of 30." McKee added, "Thanks to the generosity of our brain donor families, we now better understand the earliest stages of CTE, and it is bringing us closer than ever to diagnosing it during life." She also said, "My team and I are fully dedicated to finding effective treatments and a cure for CTE."

Chronic traumatic encephalopathy is a condition that can only be diagnosed by studying the brain tissue of a deceased individual and has been linked to repeated head impacts and traumatic brain injuries. Chris Nowinski, CEO of the Concussion & CTE Foundation, commented on the diagnosis, stating, "Mr. Kneeland played in the modern era of concussion protocols and better helmets, and yet he still developed CTE."

Nowinski said, "We have no reason to believe the current generation is at a lower risk of CTE than previous generations." He also stated, "Concussion protocols do not prevent CTE, because CTE is caused by repeated head impacts, not just concussions." Nowinski added, "If we want to reduce CTE risk, we must implement CTE prevention protocols and aggressively reduce the number and strength of head impacts at every level of the game." Kneeland began playing tackle football at age 7 and played college football at Western Michigan University.

Mancera said, "While this diagnosis does not change the tragedy of his passing, it provides important context about some of the struggles he may have been facing." She added, "We share this information to help people understand what NFL and other high contact sport athletes might be struggling with." Mancera also stated, "Raising awareness is important to us." She said, "We continue to remember Marshawn with compassion for the person he was, rather than defining him by the final moments of his life."