An accidental overdose of heroin caused the Aug. 5 death of Garrett Reid, son of Eagles head coach Andy Reid, Northampton County Coroner Zachary Lysek announced at an afternoon news conference.
The cause of death will be listed as "acute opiate (heroin) toxicity" and classified as "accidental," Lysek said.
The finding confirms what many, including the coach himself, suspected, because of Garrett Reid's history of drug abuse.
The body of Garrett Reid, 29, was found in a Lehigh University dormitory room during Eagles training camp. He was working for the club as a strength and conditioning coach, and had been involved with the team since his 2009 release from prison.
No signs of suicide or foul play were found at the time, authorities said in early August.
Northampton County District Attorney John M. Morganelli, who introduced Lysek, said that investigators did find drug paraphernalia at the scene, a syringe, a spoon and prescription medications.
Further searches of Garrett Reid's apartment and belongings found 47 syringes and needles in a gym bag, as well as 19 vials of an unknown substance.
Investigators, working with Philadelphia police, were continuing to try to determine who may have been supplying Garrett Reid with drugs, Morganelli said.
After a 7:20 a.m. 911 call, police soon found Reid's body on the floor of the dorm room, with a defibrillator nearby. An Eagles team physician had moved the young man from a chair to the floor, where an attempt was made to resuscitate him, Morganelli said.
Shortly after the death, Andy Reid released a statement alluding that drug use likely played a role. Reid said his son "lost the battle that has been ongoing for the last eight years."
In January 2007, after a car accident that injured another person, the eldest of Reid's five children admitted using heroin, then failed drug tests prior to being sentenced to two to 23 months behind bars. Later that year, he was charged with trying to smuggle prescription drugs into jail, and in May 2009 tested positive after a furlough from a treatment center. That led to a stint in Graterford Prison.
His parents, Andy and Tammy, had him seek treatment at various rehabilitation centers, and to those around the Eagles, Garrett Reid appeared to be winning the battle, so his death at such a young age stunned many.
Although the district attorney's conclusion comes more than two months after the death, it is still within a normal time frame for investigations that involve toxicology testing.
Such testing often requires a series of followups, as blood, urine and other samples are analyzed for many substances.
Frank Kummer of the Philly.com Breaking News Desk contributed to this article.