LOS ANGELES, CA (Catholic Online) - Police say the 25-year-old Belcher shot and killed his girlfriend Saturday morning before going to the team stadium and committing suicide by a self-inflicted gunshot wound as he talked to coaches.

Chiefs chairman Clark Hunt maintains that Belcher was "a player who had not had a long concussion history," even though he was a three-time all-America wrestler and a star on the football team at his West Babylon, N.Y., high school.

The cause of the Belcher tragedy has not yet been determined, but the incident has highlighted other suicides by NFL players. 

Of the 85 brains donated by the families of deceased veterans and athletes with histories of repeated head trauma, Boston University's Center for the Study of Traumatic Encephalopathy found CTE in 68 of them. Thirty-four were professional football players, nine others played college football and six played only high school football.

Surprisingly, of the 35 professional football players' brains donated, only one had no evidence of the disease, according to the study.

Boston University researchers have divided CTE, or chronic traumatic encephalopathy into four stages. The first of which involves headaches. The final stages involve "full-blown dementia." The condition has been found to involve brain tissue degeneration and a buildup of an abnormal protein called tao, found in patients with Alzheimer's disease.

Researchers say they have not yet determined how much brain trauma results in CTE. "While it remains unknown what level of exposure to brain trauma is required to trigger CTE, there is no available evidence that occasional, isolated or well-managed concussions give rise to CTE," one of the study's co-authors, Dr. Robert Cantu, said in a press release.

Belcher's suicide resembled those of former NFL players 43-year-old Junior Seau and 50-year-old Dave Duerson both he died from self-inflicted gunshot wounds to the chest in the last two years. Duerson's brain is being studied at the Boston University research center, where researchers have already learned that he had CTE.

Other notable NFL suicides include former Pittsburgh Steelers player Terry Long, who killed himself by drinking antifreeze, and former Philadelphia Eagles player Andre Waters shot himself in the head. Both suffered from CTE.

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