Adams was taken to the emergency room at Self Regional Hospital in Greenwood, where was pronounced dead, the Greenville News first reported. A preliminary autopsy Sunday revealed Adams had an enlarged heart and likely died of cardiac arrest, ESPN reported.
According to NFL Network, Coursey explained that "health issues" on Sunday morning prompted Adams' girlfriend to call an ambulance. Adams arrived at the hospital just after 8 a.m. ET and was pronounced dead less than a half hour later. Coursey said Adams had no history of health problems.
"We are stunned and saddened by the news of Gaines' passing," the Bears franchise said in a statement. "Our prayers are with his family during this difficult time."
"I just couldn't believe it was Gaines," said Tommy Bowden, who was Gaines' head coach at Clemson. "I will always remember the smile he had on his face and I will always remember his patience."
The Tampa Bay Buccaneers chose him with the fourth overall pick in the 2007 NFL draft. The Buccaneers traded Adams to the Bears during the 2009 regular season.
In his three-year NFL career, Adams played in 47 games and recorded 13.5 sacks.