This article originally appeared on Fortune.com.
Former New England Patriots tight end Aaron Hernandez, who committed suicide in April, had a severe form of a degenerative brain disease that has been linked to repeated blows to the head. Hernandez, who was serving a life sentence for murder, has joined a growing list of ex-NFL football players, including Jovan Belcher, Ray Easterling, Junior Seau, and Andre Waters, who took their own lives and were later found to have had disease.
CTE, or chronic traumatic encephalopathy, occur in four stages and can appear years after an athlete, including high school and college players, experience repetitive brain trauma such as concussions.
Jose Baez, a lawyer for Hernandez, announced during a press conference Thursday that researchers found he had a severe form of CTE. Baez also said that Hernandez’s daughter is suing the NFL and the New England Patriots for $20 million. The lawsuit was filed in federal court in Boston on Thursday, ESPN reported.
We are holding a press conference today at 4pm to disclose the latest on Aaron Hernandez death investigation #AaronHernandez— Jose Baez (@BaezLaw) September 21, 2017
Hernandez’ case stands out because of the severity of the disease in a young person. Hernandez was only 27 when he hung himself in a prison cell.
Earlier this year, a survey published by a neuropathologist in the The Journal of the American Medical Association found widespread evidence of C.T.E. in former NFL players. Dr. Ann McKee examined 202 deceased players of American football from a brain donation program. CTE was diagnosed in 177 players across all levels of play, including 110 of 111 former NFL players.
McKee, who is the director of the CTE Center at Boston University, found that Hernandez had stage three of the disease and also had early brain atrophy.