A source told Action News on Thursday morning that 29-year-old Garrett Reid died from an accidental heroin overdose.
Further details will be released at an afternoon news conference with Northampton County District Attorney John Morganelli.
Watch the news conference live at 2:00 p.m. on 6abc and 6abc.com.
Garrett Reid was found dead in his dorm room on Aug. 5 at Lehigh University in Easton, where he was assisting the team's strength and conditioning coach during training camp.
Garrett Reid's addiction first became public in 2007 when he admitted he was high on heroin when he ran a red light while driving his Jeep and rammed a car.
For Garrett and his family there came a serious of arrests and re-arrests for probation violations, and the smuggling of drugs into his jail cell.
Five years ago in court, Garrett Reid told a judge "I don't want to die doing drugs. I don't want to be that kid who was the son of the head coach of the Eagles, who was spoiled and on drugs and OD'ed and just faded into oblivion."
Shortly after Garrett's death, Andy Reid indicated that his son may have had a relapse.
Some 900 people attended Garrett Reid's funeral.
The mourners included notable names from the Eagles and the across the NFL, including quarterback Michael Vick, former quarterback Ron Jaworski, NFL Commissioner Roger Goodell and Patriots head coach Bill Belichick.