Dave Duerson NFL CongressAPDuerson and former Cowboy Darryl Johnston testify before Congress in 2007.

Football fans were saddened to learn of the death of former Chicago Bear Dave Duerson on Thursday, but now they may be outraged to hear that the 50-year-old committed suicide — and he believed that brain injuries from playing football might be to blame.

Last night, the Miami-Dade County medical examiner ruled Dureson's death a suicide, from a self-inflicted gunshot wound to the chest.

In addition, NBC Chicago reports that Duerson sent to a text message to his loved ones asking that his brain be donated to NFL research after his death.

Duerson's brain will in fact be sent to Boston University's Center for the Study of Traumatic Encephalopathy. They have previously studied the brains of 14 NFL players and 13 of them were found to have CTE, a degenerative brain disease similar to Alzheimer's.

The news comes at a key time in the NFL labor negotiations as one of the biggest sticking points continues to be the 18-game NFL season. The league insists it's taking head trauma and player safety seriously, but it's hard to see how adding two more full contact games to the schedule doesn't increase the risk for more players to end up like Duerson.

The player's association need only point to him and Andre Waters (and get James Harrison to stop saying he wants to hurt people) to make their case for not lengthening the season just yet.

In 2007, Duerson testified before the Senate Commerce Committee to discuss the NFL retirement plan and long term injuries.