The brain of former Kansas City Chiefs linebacker Jovan Belcher — the 25-year-old player who shot and killed his girlfriend in 2012 before committing suicide — showed signs of pervasive brain damage like that found in other deceased NFL players, according to a neuropathologist.

In a report obtained by "Outside the Lines," Dr. Piotr Kozlowski writes that he detected neurofibrillary tangles of tau protein, which is identified with chronic traumatic encephalopathy. The tangles were distributed throughout Belcher's hippocampus, an area of the brain involved with memory, learning and emotion.

Dozens of former NFL players have been diagnosed posthumously with CTE, a neurodegenerative disease linked to dementia, memory loss and depression. The disease, researchers say, is triggered by repeated head trauma.

On Dec. 1, 2012, Belcher shot and killed girlfriend Kasandra Perkins, the mother of his then-3-month-old daughter. Belcher then drove to the Chiefs' practice facility, where he shot himself in front of team officials in the parking lot. While the murder-suicide reignited the debate over athletes and guns, it also increased the focus on a frequently overlooked issue at the time: the NFL's domestic violence problem.