Sage Stallone's cause of death a heart attack - report

Sylvester Stallone's son Sage Stallone was found dead July 13 at the age of 36 and there has been much speculation about the cause, including rumors of drugs. But according to TMZ, the Los Angeles County Coroner has determined Stallone died of natural causes after suffering a heart attack.

No drugs were found in Stallone's system and in fact there was evidence of heart disease, which a source at the coroner's office says is "unusual" for a person of his age.

It's been a tough summer for the Stallone family. Sylvester and his brother Frank (pictured right, with Sage) lost Sage back in July and just this week their half-sister Toni-Ann passed away after a battle with lung cancer.