Sylvester Stallone's Son: Cause of Death Revealed

Sage Stallone

Sage Stallone Died of a Heart Attack, Not a Drug Overdose

Sylvester Stallone's son, Sage Stallone, did not die from a drug overdose, as was rumored.

The L.A. County Coroner has released the cause of death for Stallone, who died of natural causes.

Stallone died from a heart attack, due to evidence of atherosclerotic coronary artery disease.

Read: Sylvester Stallone's Half-Sister Dies Just Weeks After Son Sage

A source tells TMZ that it was "unusual" for someone Stallone's age to have such advanced coronary problems.

He was said to have "sub-therapeutic" levels of Vicodin in his system.

Stallone died at age 36. His body was found on July 13 in his home; investigators found drug paraphernalia, including more than 60 large pill bottles and bags of "white powder," which fueled rumors of a drug overdose.

Read: 'The Expendables 2' Smashes Box Office

Stallone co-starred with his father in two films, making his acting debut in Rocky V and appearing in 1996's Daylight.

He directed the 2006 short Vic, which screened at the Palm Springs Film Festival.