In May 2012, former linebacker Junior Seau shot himself in his bedroom in Oceanside, California, and independent researchers later determined that he suffered from chronic traumatic encephalopathy (CTE). According to Reuters, Seau’s family filed a lawsuit against the NFL and helmet manufacturer Riddell, Inc., accusing them of wrongful death, fraud, negligence and concealment. They claim that Seau’s suicide last year was the result of the brain disease caused by violent hits he endured while playing football for 20 years.

CTE is caused by repeated impacts to the brain and has been found in athletes and members of the armed forces who have suffered head injuries. The disease can result in Alzheimer’s-like symptoms such as dementia, memory loss, aggression, and depression. However, mild and moderate brain injuries do not show up on CT scans and other imaging, so the condition can only be definitively diagnosed through an autopsy.

Seau suffered sub-concussive and concussive blows to the head throughout his NFL career. His family notes that he exhibited self-destructive, aggressive and violent behavior, suffered extreme depression and withdrew from his family and children. According to the lawsuit, Seau also began to drink and gamble to cope with depression and insomnia.

More than 1,500 former NFL players are suing the NFL, alleging the league hid the dangers of concussions from them. The lawsuit concerning Seau states that “the NFL was aware of the evidence and the risks associated with repetitive traumatic brain injuries for many decades, but deliberately ignored and actively concealed the information from the players, including the late Junior Seau.”

Although not everyone who is exposed to repeated head trauma will develop CTE, a number of other players who took their own lives, such as Dave Duerson, Shane Donett and Ray Easterling, were later diagnosed with the disease. In a recent study, researchers found CTE in 34 of 35 deceased NFL players whose brains were donated by family members.

League teams have donated $30 million to the National Institutes of Health for research on CTE and other brain injuries. Recent suicides from NFL players are raising concerns over the effects of brain injury and repeated concussions in football, the $9 billion a year industry and most popular television sport. The Seau family explained that they know this lawsuit will not bring back Junior, but it will “send a message that the NFL needs to care for its former players, acknowledge its decades of deception on the issue of head injuries and player safety, and make the game safer for future generations.”