Phillip Adams, a former NFL player accused of fatally shooting six people in South Carolina before killing himself in April, suffered from unusually severe brain disease in the frontal lobe, autopsy revealed.

The 20 years he spent playing football “definitely … gave rise” to a diagnosis of stage 2 chronic traumatic encephalopathy, said Dr. Ann McKee, who examined his brain.

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On April 7, Adams killed physician Robert Lesslie; his wife, Barbara; two of their grandchildren, 9-year-old Adah Lesslie and 5-year-old Noah Lesslie; and two HVAC technicians working at the Lesslie home, James Lewis and Robert Shook, both 38. Adams was later found with a self-inflicted gunshot wound to the head.

The degenerative disease known as CTE is linked to head trauma and concussions that has been shown to cause a range of symptoms, including violent mood swings and memory loss.

“There were inklings that he was developing clear behavioral and cognitive issues. I don’t think he snapped. It appeared to be a cumulative progressive impairment. He was getting increasingly paranoid, he was having increasing difficulties with his memory, and he was very likely having more and more impulsive behaviors. … It may not have been recognized, but I doubt that this was entirely out of the blue,” McKee said, adding that that of 24 NFL players diagnosed with the disease after dying in their 20s and 30s, most had stage 2, like Adams.

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Meanwhile, the Lesslie family said they appreciated the diagnosis.

“Even in the midst of crushing heartbreak, we are finding some comfort in the CTE results and the explanation they provide for the irrational behaviors pertaining to this tragedy,” their family statement said.