ROCK HILL, S.C.—An autopsy revealed unusually severe brain disease in the frontal lobe of the former NFL player accused of fatally shooting six people in Rock Hill, South Carolina, before killing himself in April, authorities announced Tuesday. The 20 years Phillip Adams spent playing football “definitively … gave rise” to a diagnosis of stage 2 chronic traumatic encephalopathy, said Dr. Ann McKee, who examined his brain. Authorities have said that on April 7, Phillip Adams killed Rock Hill 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. Police later found Adams 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 …