Former Dallas Cowboys defensive end tragically died by suicide in November 2025, mere months into his sophomore NFL season.
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Now, the defensive standout's cause of death has been confirmed.
Kneeland, a former second-round pick, was posthumously diagnosed with Stage 1 chronic traumatic encephalopathy (CTE).
Boston University's CTE Center made the diagnosis after Kneeland's family donated his brain for research. There are four stages of CTE, with Stage 4 showing the most damage.
In the wake of his diagnosis, Kneeland's family also released a statement.
"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," the statement read. "We share this information to help people understand what NFL and other high-contact sport athletes might be struggling with. 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."
Dr. Ann McKee, director of the Boston University CTE Center and chief of neuropathology for the VA Boston Healthcare System, discussed the diagnosis in more detail.
"Unfortunately, I was not surprised to find CTE in the brain of Mr. Kneeland. We have found this progressive brain disease in nearly half of the athletes we've studied who have died before the age of 30," said McKee.
Even with improved helmets and concussion protocols, NFL athletes remain at risk of developing CTE.
"Mr. Kneeland played in the modern era of concussion protocols and better helmets. Yet, he still developed CTE," Dr. Chris Nowinski, Concussion & CTE Foundation CEO, added.
Marshawn Kneeland Played Two Seasons For the Dallas Cowboys
Kneeland was selected by the Dallas Cowboys in the second round of the 2024 NFL Draft following a standout collegiate career at Western Michigan.
Kneeland played parts of five seasons with the Broncos. He was named second-team All-MAC during a senior year that saw him record 4.5 sacks, 7.5 tackles for loss and 2 forced fumbles.
He also earned a trip to the 2024 Senior Bowl.
Two days before his death, Kneeland had one of the biggest games of his career, in which he recovered a blocked punt and scored a touchdown.
Kneeland's former defensive coordinator Mike Zimmer described the late defensive end as a "great person" who "loved playing the game."
"He was a great person. Always eager to learn and wanted to be great. He didn't take any crap from anyone on the field. He studied hard and loved playing the game," Zimmer said.
