“CTE is linked to repetitive brain trauma and has a distinct pathology that can only be diagnosed at autopsy,” says Dr. Ross Zafonte, a principal investigator of the Football Players Health Study at Harvard University and executive vice dean at the University of Missouri School of Medicine.

The man who killed four people in the New York City skyscraper that is home to NFL headquarters carried a note blaming the league for his mental health problems.

A former high school football player who opened fire in a Manhattan building Monday — killing four people before fatally shooting himself — left a note seemingly blaming the NFL for giving him a brain disease,