Marshawn Kneeland, a defensive end for the Dallas Cowboys, was posthumously diagnosed with stage 1 chronic traumatic encephalopathy (CTE) following his death by suicide in November 2025.
The diagnosis was announced on Tuesday, July 7, by his family through the Concussion & CTE Foundation after researchers at the Boston University CTE Center examined his donated brain tissue.
Kneeland, who was 24 years old at the time of his death, had been selected by the Cowboys in the second round (56th overall) of the 2024 NFL Draft out of Western Michigan University. He began playing tackle football at age 7 and appeared in 18 NFL games over his first 1.5 professional seasons.
Kneeland died on November 6, 2025, from an apparent self-inflicted gunshot wound. The incident followed a police pursuit that began late on November 5 in the Dallas area. Texas Department of Public Safety troopers attempted to stop his vehicle for a traffic violation involving high speeds exceeding 145 mph and unsafe lane changes on the Dallas North Tollway. The pursuit continued into Frisco, where the vehicle crashed.
Kneeland fled on foot, and authorities, including Frisco police, later located him deceased. Police had received information during the pursuit that Kneeland had previously expressed suicidal thoughts. Two days prior to his death, he had played 17 snaps in a Cowboys game against the Arizona Cardinals.
Kneeland’s family released the results of the post-mortem brain tissue analysis conducted by the Boston University CTE Center. The analysis determined he had stage 1 CTE, the lowest level on a diagnostic scale of 1 to 4. Stage 1 represents the earliest and mildest form of the condition
“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,” Dr. Ann McKee, director of the Boston University CTE Center and chief of neuropathology for the VA Boston Healthcare System, told Pro Football Focus.
“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. My team and I are fully dedicated to finding effective treatments and a cure for CTE,” she added.
Kneeland’s family also issued a statement following the diagnosis. “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. We share this information to help people understand what NFL and other high contact sport athletes might be struggling with,” the family said.
“Raising awareness is important to us. We continue to remember Marshawn with compassion for the person he was, rather than defining him by the final moments of his life. One Love,” they added. The family requested privacy and indicated they would not participate in interviews.
Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease linked to repeated head impacts, such as those experienced in contact sports including football. It is characterized by the abnormal accumulation of tau protein in the brain, which leads to the death of nerve cells and progressive brain atrophy over time, according to the Concussion & CTE Foundation.
CTE can only be definitively diagnosed after death through neuropathological examination of brain tissue, as there is currently no reliable method for diagnosis during life.
Symptoms associated with CTE, which may appear years or decades after exposure to head impacts, can include cognitive impairment (such as memory loss and executive dysfunction), mood and behavioral changes (including depression, irritability, impulsivity, and aggression), and motor symptoms in later stages. Research indicates a strong association between repetitive head trauma and CTE development.
