Sports fans were shocked, but probably not surprised, to hear that former New England Patriots star Aaron Hernandez had a severe case of CTE. Its formal name is Chronic Traumatic Encephalopathy. Whatever it’s called, however, CTE is a living hell for sufferers and their loved ones as well.

As you may recall, Hernandez was in prison for murder when he hanged himself in his cell. He was only 27. Let that sink in. Only 27. Yet a researcher at the CTE Center in Boston stated that Hernandez’s condition was already severe, at stage 3 of 4. In addition, Hernandez’s attorney, Jose Baez, said, “We’re told it was the most severe case they had ever seen for someone of Aaron’s age.”

Moreover, Dr. Bennet Omalu, who drove extensive research into the relationship between football and CTE, believes that CTE accounted for Hernandez’s violent streak, as well as his suicide. He said:

“I am yet to examine the brain of professional football player who does not have CTE or other forms of brain damage. And we have always known for centuries that if you suffer forceful and/or repetitive blows to your head in whatever human activity, you will suffer brain damage.”

So what is CTE, and what does it do to the brain? Here’s what happens. It’s not pretty:

Now Hernandez’s family is suing the NFL and the Patriots for a whopping $20 million. The suit is on behalf of Hernandez’s 4-year-old daughter. As the lawsuit reads, in part:

“Aaron Hernandez succumbed to the symptoms of CTE. As a result of the defendants’ conduct and the injury experienced by Aaron, Avielle Hernandez was deprived of the love, affect, society and companionship of her father while he was alive.”