Updated

Former NFL star linebacker Junior Seau reportedly suffered from a brain disease, likely caused by two decades worth of blows to the head, when he killed himself last May.

Seau ended his life at his home in California with a gunshot to the chest. Many believed he shot himself in the chest to preserve his brain for testing, and his family members donated it to neuroscientists at the National Institutes for Health.

According to a report from ABC News and ESPN, Seau's family members said researchers have concluded that Seau suffered from chronic traumatic encephalopathy (CTE), a degenerative disease typically caused by multiple hits to the head.

Seau, who was just 43 years old when he died, was known as one of the hardest hitters during his 20 NFL seasons. He spent 13 years with San Diego, three with Miami and four with New England before retiring after the 2009 season.

The 12-time Pro Bowl selection is just the latest former NFL player to be diagnosed with CTE, which can only be ascertained after death.

Former NFL defensive back Dave Duerson, who played with the Chicago Bears, New York Giants and Arizona Cardinals, also killed himself in 2011 and was found to have CTE. He asked his family to donate his brain for testing.

The Seau report could also be another blow to the NFL in its ongoing issues with concussions and brain disease. Numerous lawsuits have been filed against the league by former players who have alleged the NFL knew about the dangers of concussions and other head injuries, but did nothing to protect the players.

"We appreciate the Seau family's cooperation with the National Institutes of Health," the NFL said in a statement Thursday. "The finding underscores the recognized need for additional research to accelerate a fuller understanding of CTE. The NFL, both directly and in partnership with the NIH, Centers for Disease Control and other leading organizations, is committed to supporting a wide range of independent medical and scientific research that will both address CTE and promote the long-term health and safety of athletes at all levels. The NFL clubs have already committed a $30 million research grant to the NIH, and we look forward to making decisions soon with the NFL Players Association on the investment of $100 million for medical research that is committed in the Collective Bargaining Agreement. We have work to do, and we're doing it."

NFL commissioner Roger Goodell has made player safety among his chief concerns in recent years.