Former Patriots player Aaron Hernandez had severe damage to his brain from sports-related head injuries that are known to impede decision-making and cause aggression, said a Boston University researcher who announced the pathology results today.

“In any individual, we can’t take the pathology and explain the behavior,” said Dr. Ann McKee director of the Boston University Chronic Traumatic Encephalopathy Center and chief of neuropathology for the VA Boston Healthcare System. “But we can say collectively, in our collective experience, that individuals with CTE and CTE of this severity have difficulty with impulse control, decision making, inhibition or impulses or aggression, often emotional volatility and rage behavior.”

McKee presented the post-mortem study this afternoon, with images of the former player’s brain that showed extreme tissue loss with evidence of “microbleeds” associated with head trauma.

“These are very unusual findings for someone so young,” she said, noting other brains with similar damage came from men at least 20 years older.

The BU center has pioneered the study of NFL players' brains, finding severe damage caused by repeated concussions.

Hernandez, 27, committed suicide earlier this year in his Massachusetts prison cell, where he was serving a life sentence for murder. Days before, he had been acquitted of two other murders. Lawyers for his estate have contended he suffered brain damage during his time playing football.